These are the Chocolate Chip Cookies of my dreams! It only took 48 attempts. Superior crispy outsides, soft-baked insides, excellent chewiness, intensely buttery with butterscotch tones, exceptional shelf life. A copycat of Australia’s famous Butter Boy cookies – but better!
On a personal note, thank you to everyone who left such kind, supporting messages on my burn out post a couple of months ago. I am back! Well rested, I have a new assistant, much has happened, and I will do a catch up post next week!
The Chocolate Chip Cookies of my dreams
These started out as a simple copycat of the milk choc cookies from Butter Boy, a popular cookie shop here in Sydney. I feel like I’ve tried my fair share of internet-famous cookies, and these are the first that have lived up to the hype.
But at $8.50 a pop, making a homemade version was a no brainer! Plus, I was able to tweak them to my own taste – such as making them a bit less sweet (the Butter Boy ones are so sweet!), more buttery flavour – and most importantly, a version that can be made in regular home kitchens.
It took 48 attempts, creating it then retesting and stress testing iterations. But it was worth it! I’m thrilled with the final result, my ultimate chocolate chip cookies that are everything I dream a cookie to be!
They boast a rich, buttery flavor with deep butterscotch undertones, thanks to browned butter (which is literally just simmered melted butter). This simple magic ingredient ensures incredible taste, whether you use budget-friendly or premium butter.
Superior texture – thick crisp, golden crust with soft, chewy insides. Their generous size allows for a long enough bake to create an excellent crispy surface while keeping the centre irresistibly gooey which is ultra soft and moist but not blatantly raw cookie dough (not a fan of raw flour taste);
Every aspect of these cookies is elevated by an overnight dough chill – flavour, crispiness, chew, colour, and even shelf life. I’ve tested so many with and without chilling, and shorter fridge times to compare side by side. I’m now a believer – there’s simply no way to cheat time!
They cost 70% less than the Butter Boy cookies. And in my humble opinion, they taste better. I would be delighted to hear thoughts from Butter Boy die-hard fans who try this recipe!
PS These cookies are BIG. Intentional, so they can be baked long enough to develop a great crispy crust while keeping the inside soft-baked.
11cm / 4.5″ wide2.5cm / 1″ thick
Also – proof of crispy base and soft baked insides (I pressed with my finger so you can see it’s not cakey, dry or crumbly):
Crispy golden base!Inside of the cookie – I pressed with finger to show it’s moist.
Ingredients in The Chocolate Chip Cookies
Here’s what you need to make these. No unusual ingredients, achieving the perfect outcome came down to a very exact amount of each ingredient. See FAQ for more information – like can you reduce sugar (no!), can these be made gluten free (sadly not!).
For the cookie dough
Plain flour / all purpose flour – Please do not substitute with self raising flour. This recipe calls for a much lessor amount of baking powder than what is built into self raising flour.
Brown and white sugar – Each of these bring different qualities to cookies. The brown sugar adds colour, chew and caramely flavour, while the white sugar makes the cookies crispy. I use caster sugar (superfine sugar) as it dissolves more easily in baked goods as the grains are finer so it is my default sugar for baked goods. However, regular white sugar (granulated sugar) also works fine.
Unsalted butter – Chopped into pieces so it melts more evenly as we are browning the butter. I prefer to use unsalted butter so I can control the amount of salt added into the recipe.
Cooking salt – I use 1/2 teaspoon of salt in these cookies which may sound like a lot but it really works here to offset the sweetness and enhance all the incredible flavours in this cookie. Trust the process! See recipe notes for using table salt and salt flakes.
Egg + egg yolk – Using an egg yolk in place of a second whole egg adds richness, plus to be honest, I didn’t need a whole second egg and it’s easier to measure out a yolk than 1/2 an egg. Make sure you use large eggs which are 50-55g / 2oz each in the shell, sold in cartons labelled “large eggs”. If you only have jumbo or XL eggs, see this post for how to measure out the correct amount.
Baking powder and baking soda (bi-carbonate) – In cookies, baking powder makes them rise, while baking soda makes them spread, so don’t swap them! After much testing, I found 1/4 tsp baking powder and 1/2 tsp baking soda created the perfect shape and texture.
Cornflour / cornstarch – A baking trick I picked up in my time, a little cornflour softens the inside of cookies without affecting the crispy exterior. Plus, adjusting the amount controls their shape – just 1 tablespoon extra turns it into a big dome shape!
Vanilla – For flavour. Vanilla extract please, not imitation essence.
The choc chips
Chocolate chips are key in chocolate chip cookies! So unsurprisingly, I have thoughts. I tried chopped chocolate but preferred chips for these big cookies – they disperse better throughout rather than having larger chunks but less of them.
I mix dark and milk chocolate for balanced sweetness – 250g dark (semi-sweet) and 150g milk chocolate chips (which are much sweeter than dark chocolate). Since standard Aussie choc chip packs are 200g, feel free to just use one pack of each or use chopped chocolate instead!
These cookies must be refrigerated for 12 hours. Sorry!
Once I landed on my “perfect” cookie recipe that required an overnight chill, I was sure I could tweak it to be just as good (or 98% as good) with only an hour or so in the fridge.
I really tried. (48 versions, remember!). But I was wrong. Once you’ve had the overnight chilled version, there’s no going back. The best I got was 90% as good – turns out, you can’t cheat time!
what does refrigerating cookie dough do?
It improves virtually every aspect of this cookie:
flavour develops
outside bakes up crisper
inside is chewier
colour is a richer golden colour
cookie surface bakes up nicer
shelf life is superior. Excellent 3 days, still great 5 days. The shelf life quality reduces for shorter fridge times. Regular choc chip cookie recipes are noticeably stale on day 3, I find.
flour is hydrated and butter solidifies so the cookies bake thick with soft baked centre rather than spreading thin and crispy
DIFFERENT COOKING DOUGH CHILL TIMES
Here is how the cookie is affected by different cookie dough chill times:
1 hour (good) – bare minimum chill time, cookie works and is tasty. It is not as golden and there is a faint crackly skin on the edges if you look closely, which I do! There is also noticeably less chew than the 12 hour dough chill. Personally I’d make Browned Butter Choc Oatmeal Cookies instead.
5 hours (better, closer to best) – minimum chill time I will make these, company worthy!
12 to 24 hours– best, the base recipe!
24 to 48 hours – just as great, but need to be really sure cookies are in a super airtight container as the dough is susceptible to drying out (I cover with cling wrap in an airtight container.
Beyond 48 hours – diminishing returns plus higher risk of dough drying out on the surface (beyond 4 days I would also query food safety). Better to freeze after 12 hours.
Freezing – The raw dough can be frozen after doing the 12 to 24 hours fridge chill. Put the dough discs into airtight containers, cling wrap or ziplock bags and freeze for up to 3 months. Bake from frozen or thaw then bake (I do this because they are exactly like the original. Cookies baked from frozen are a bit thicker and slightly less crispy on the base).
Note: You still need to do the fridge time before freezing as all the above listed good things that happen to cookie dough in the fridge can’t happen when frozen rock solid.
How to make The Chocolate Chip Cookies
Are you ready to see how straightforward it is to make the Chocolate Chip Cookie of your dreams??
1. BROWN THE BUTTER
Browning butter is as simple as melting butter then letting it simmer until it changes from yellow to golden brown which only takes a few minutes. This intensifies the buttery flavour and makes the cookies taste buterscotchy. For this recipe, it’s important because it levels the playing field whether making this cookie with economical or premium butter.
Melt butter in a silver or other non-black saucepan or small pan. Simmer the melted butter on medium to medium high for 3 to 5 minutes or until you see little golden bits (which are the dairy bits that go toasty) and you can smell the nuttiness. The butter will also change from yellow to golden brown in colour.
Why does the colour of the cooking vessel matter? It’s easier to see when the butter changes from yellow to golden. If using a black pan, you need to rely on your smell or using a spoon to scoop the butter up to check the colour.
Remove from the stove and immediately pour it into a large mixing bowl (including all the little brown bits – extra flavour!). Work quickly as it will continue browning. Then let it cool for 45 minutes+ to room temperature.
Cooling – The browned butter should still be liquid (ie not solidified bits, not even around the edges) but cool enough so it will not melt the sugar or the choc chips. If it solidifies, then re-melt in the microwave and cool again.
2. The dough is so easy!
You just need a wooden spoon, no stand mixer!
Whisk Dry ingredients in a bowl.
Wet ingredients – To the cooled brown butter, mix in both sugars using a wooden spoon. It will look like wet sand. Then add the egg, yolk and vanilla and mix. It will look like a a thick caramel (but with visible fine sugar grains).
Make dough – Add the flour into the butter bowl and mix. When the flour is mostly incorporated, add the choc chips then mix well until all the flour is fully incorporated.
FAT DISCS not balls (and they’re BIG!) – Divide the mixture into 8 equal mounds. They will be 1/2 cup slightly heaped / 155g each (5.3 oz). Roll into balls to properly seal all cracks (which will split during baking) then shape into a fat disc 3.75cm/1.5″ thick. See FAQ for chatter about this shape and why shape before chilling.
Don’t worry if no choc chips are visible on the surface, we will add more for decorating once baked. Don’t try pressing extra choc chips onto the dough after after shaping, they will likely split and form unsightly crevices when the cookies bake. Mega cookies behave differently to regular cookies – they are prima donnas! Smaller cookies? Absolutely. They work really well for small cookies, say 1 to 3 tbsp (20 – 60g / ~0.7 – 2 oz) but be sure to roll into balls instead of flattening into discs. The bake time is 12 to 14 minutes (see recipe card for
Fridge 12 – 24 hours – Put the discs in an airtight container and refrigerate for 12 to 24 hours. See section above for why refrigerating is necessary and how hard I tried to avoid it!
Chill time variations): – 1 hour is the bare minimum (personally I’d make Browned Butter Choc Oatmeal Cookies instead) – 8 hours is my minimum – 12 – 24 hours is optimal, up to 48 hours – Beyond 48 hours: diminishing returns plus dough starts to dry out, better to freeze after 12 hours.
Bake 17 minutes – Preheat the oven to 180°C/350°F (170°C fan-forced)*. Once the oven is hot, place the fridge cold cookies on a paper lined tray 7.5 cm / 3″ apart (to allow for spread).
Bake for 17 minutes, checking first at 16 minutes**, until the outside edges are golden and the surface is pale golden but has a thin baked skin on it (ie not just shiny melty raw dough). They will look underdone (you will spy wet batter through cracks) which is what you want to allow for carry over cooking as they cool down, by which time they are perfect – soft baked inside, ultra crispy outsides!
* Not, it’s not a typo! It is 170°C fan or 180°C conventional oven, only 10°C difference rather than the usual 20°C. 190°C conventional browns too much on the edges. ** The cookies may bake faster for any number of reasons – like if your oven runs hot or is preheated for a long time, or if you use flimsy trays. So check first at 16 minutes. Mine take 17 minutes.
Bake one tray at a time in regular size ovens (60cm / 24″) to allow plenty of air circulation for even baking of the cookies. If you have a large 90cm / 35″ oven, you can bake 2 trays at a time.
Decorate – Working quickly, press extra chocolate chips on the surface. I like to press them in slightly, some straight, some wonky. But even if you just place them on top, the heat will melt the chocolate so they bond.
TIP: While still hot, you can also use a spatular to reshape wonky ones into neat circles.
Cool the cookies on the tray for 20 minutes. During this time, the inside will also finish cooking, the surface becomes more golden, and the outside and base becomes super crispy.
ATTACK! The 20 minutes mark straight out of the oven is the prime moment of perfection to devour these cookies, when the inside is still warm and the chocolate is molten and gooey, but the outside has set enough so it’s gorgeously crispy. Grab one right now!!!
Phew! So that’s it. The Chocolate Chip Cookies of my dreams. 3 months and 43 versions later. That’s:
Make these once, and I wager they will invade your dreams every night too! – Nagi x
FAQ – The Chocolate Chip Cookies of my dreams
The shelf life is incredible!! And the overnight refrigeration is one of the reasons – I specifically tested this and was amazed at the difference. These cookies are:
100% prime cookie perfection 20 minutes out of the oven (still warm, melty chocolate, ultra crispy edges);
98% as good for 2 hour after;
97% as good for the next 24 hours;
Day 2 – 96% as good (most cookies are 80 – 85%). In particular so impressed with how well the crisp edges and chewiness hold up!
Day 3 – 92% as good, still company worthy in my books (regular cookies start to show signs of staleness at this point)
Days 4 to 5 – still incredibly good and enjoyable! They can also be revived with a 5 minute bake.
Don’t you hate it when you see a cookie recipe and get all excited, only to find out there’s a 12 hour chilling time?? Sooo annoying, especially when you want cookies NOW!
Why we chill dough – It improves flavour, texture, colour and affects the shape of a cookie if a recipe, like this one, is created where chilling is a necessary step. The flour absorbs liquid which firms up the dough and makes cookies bake thicker.
If I made this cookie so it didn’t need chilling, I would have used a lower hydration and the cookie would not taste the same or have the same texture inside – or outside, for that matter. Certainly less buttery, less rich and less delicious!!
I haven’t tried with gluten free flour yet but I suspect they will not work without further testing and alterations to the recipe.
Because the ball are big and solidify into rocks when refrigerated and they kept coming out of the oven with a hump in the middle. I tried lowering the temp to give them spreading time (lacked crispiness and colour), de-chilling to soften (variable too great – difference between just-soft and quite soft had a massive impact on baked shape and right oven temp).
Because if you chill the dough in the bowl, it solidifies into an un-scoopable mass. So you need to leave it out to soften until scoop-able, roll the balls, shape into discs, then chill it again until they firm up else they will spread too much in the fridge.
It’s just easier to shape before chilling!
The recipe calls for a specific baking temperature of 180°C/350°F (170°C fan-forced). Usually, the difference between fan and conventional ovens is 20°C, so 170°C fan would be 190°C/375°F. (I bake using a fan-forced oven, common here in Australia). However, I found this was too hot for these cookies, they browned too much on the outside.
No! Not for this recipe! Sugar plays an important part in baking science and the success / failure of baked goods. In particular for this recipe, I fiddled with the sugar amount and proportions of white v brown sugar v dark brown sugar over 20 times before landing on the final quantities!
The recipe calls for 1 cup brown sugar and 1/2 cup white sugar which is a lot for 8 cookies (I told you, these are not for the faint hearted!!). I tried so many iterations with less sugar because my natural palette errs towards the less-sweet end for baked goods and I do find the Butter Boy Cookies overly sweet.
But the end result wasn’t as good – less crisp, didn’t spread properly, baking into unflattering “UFO” shapes etc.
In fact, the better part of 20 versions of this recipe used 3/4 of the sugar in the final recipe, but I just couldn’t achieve the outcome I was after. Dialled it back up…and bam! Solved.
If you reduce the sugar the cookie won’t be as crispy, as golden, and bakes thicker with a hump in the middle. If this doesn’t bother you, feel free to give it a go!
I have not tried with sweeteners so I have no idea how they will impact this cookie.
Err…yes. I know. I’m a little mad. In fact, I believe the press have called it “obsessive testing”. I’m ok to own it. I know I have a problem. Not being able to crack something I set my sights on irritates me so much, it keeps me up late into the night, thinking about it, researching, analysing the testing I’ve already done, and also just lying there annoyed that I haven’t cracked it.
To be honest though, I landed on the a recipe I was very happy with probably at around version 7, and it was excellent, quite similar to the final version though a little more rustic looking.
But it called for an overnight fridge chill, and I was cocky enough back then to think that I could crack the code to make a version 98% as good without an overnight fridge chill.
48 versions later, I can say I was wrong.
I got to about 90%, but no matter what I did, no matter what tricks I pulled out, and even though the cookie – by regular chocolate chip cookie recipe standards – was still excellent, it was not as good as the overnight chilled cookie.
As I outline in the post, overnight chilling does things to the dough that you can’t cheat or replicate with shortcuts, much like great sourdoughs and pizzas are left to prove for days to develop extra flavour. The cookie develops better flavour, it’s chewier (this is really noticeable), the crust bakes up thicker and stronger and and longer lasting (days!), the surface colour of the cookie is a beautiful rich golden brown colour that you will never achieve for a cookie of this size without hours of resting time.
The most remarkable discovery though was what it does to shelf life. The cookie is still excellent at 5 days – texture wise, flavour wise and freshness. The cookies I baked without 12 hour fridge chilling didn’t come close.
Another thing that had me tearing my hair out was trying to use less sugar. These cookies are rich and sweet, and I really wanted to dial back the sweetness a bit because I don’t usually use this much sugar in cookies!
But, after quite a few attempts, turns out it wasn’t possible to do without compromising the end result – see the “sugar” FAQ for more chatter about this.
This recipe can be made with cup and spoon measures whatever country you are in with the exception of Japan, please use the weights provided (Japanese cups are much smaller).
Did you know – Cup sizes differ slightly between the US (1 cup = 236ml / 8 oz) and the rest of the world (250 ml). While the difference is not enough to make a difference in most recipes, for some baking recipes it can mean the difference between success and failure. Especially for cookies recipes. Ever had an epic fail using a cookie recipe from an author in another country?
You don’t need to worry about that for this recipe. I’ve made it using US cups (236ml / 8 oz), Australia/rest of world cups (250 ml) and the weights provided and there was no difference in the end result. So you can make this recipe as is, without any alterations.
It sure can! Be sure to do a minimum 12 hour fridge chill before freezing, and make sure the dough discs are in a very airtight container so they don’t dry out. They can be baked from frozen (same temps as the recipe, adding an extra 1 – 2 minutes) though the cookies will be a little thicker than pictured.
I prefer to thaw them overnight in the fridge, then bake per the recipe because the cookies come out exactly as per the base recipe. If you thaw on the counter and they become soft, you need to refrigerate again until they are rock hard.
Servings8big cookies (11 cm/4.5″ wide, 2.5cm/1″ thick, 150g/5oz each!)
Tap or hover to scale
Recipe video. These are my idea of the perfect chocolate chip cookie – superior crispy outsides, soft baked inside with excellent chew, buttery with butterscotch tones and a milk-dark chocolate combo that’s just right. And they’re BIG (2.5cm/1″ thick, 11cm/4.5″ wide) – intended for high impact!Inspired by Australia’s famous Butter Boy milk choc cookies, it took me 48 attempts to perfect these. For best results, do not skip the 12 hour dough chill, but see note 5 for reducing the time. See Trouble Shooting accordion below recipe card for extra tips.PS You will make me very happy and guarantee success if you use scales. If you don’t, please read Note 1 for measuring flour!PPS Yes it’s over 4 cups of chocolate chips. I told you, these are BIG and OUTRAGEOUS! I still think I use less chocolate than Butter Boy though
Prevent screen from sleeping
Instructions
ABBREVIATED RECIPE:
Brown butter, cool, hand mix in sugar, then egg + vanilla. Mix in whisked Dry, adding choc towards end. Form 8 x 155g (1/2 cup) discs 3.75cm/1.5″ thick. Fridge 12 -24 hrs. Bake from fridge cold 4 at a time, 180°C/350°F (170°C fan) 17 min, top with more choc while hot if desired. Cool 20 min on tray, attack!
Browned butter:
Simmer to brown – Put the butter in a silver saucepan or small pan over medium high heat. Once melted, let it simmer (as in, bubbling) for 4 to 5 minutes, stirring every now and then, until it gets real foamy, you see little golden specks (wade through foam to see) and it smells nutty & extra buttery.
Cool – Immediately pour into a heatproof bowl, including all those golden specks. Cool to room temperature (~45 minutes), cool enough so it won’t melt the choc chips (Note 4)
Dough:
Whisk Dry ingredients in a separate bowl.
Mix Wet – To the browned butter, add both sugars and mix with a wooden spoon. Add the egg, yolk and vanilla. Mix until smooth – it will look caramel.
Finish dough – Add the Dry ingredients and mix until the flour is mostly incorporated. Add the choc chips and stir until the flour is fully incorporated.
Make dough discs – Measure out 8 x 155g (5.3 oz/ 1/2 cup) portions of dough, roll into a ball then shape into a 3.75cm/1.5″ thick round disc. Place in a very airtight container. (Note 5 for smaller cookies)
BAKING:
Preheat oven to 180°C/350°F (170°C fan-forced). (Note 7)
Place 4 fridge-cold cookies 7.5 cm/3″ apart on a tray lined with baking paper/parchment paper. (Note 8 baking tips)
Bake for 17 minutes or until the edges are golden and the surface is just set (ie not melty raw dough) but still pale.
Decorate and cool – Working quickly, press extra choc chips on the surface (Note 9), then cool on the tray for 20 minutes – finishes baking, edges crisp more and they get more golden all over.Tip: While hot, you can also reshape with a rubber spatula or similar into a tidy round shape.
Grab now – peak eating moment! Or, transfer to a rack to cool fully before storing in an airtight container.
Recipe Notes:
1. Measuring 225g butter without scales – don’t guesstimate using packet markings!! Melt butter and measure 235ml using a jug (or 1 cup then remove 1 tablespoon), THEN brown the butter (once browned, butter is 180 – 190g). And yes, it’s 235ml, not 225ml (1g butter = 1.043173 ml). US readers – not applicable to you, just use 2 sticks! 2. Measuring flour (important!) – Scales best (and efficient). If using cups, spoon flour into cups then level surface. Do not dunk cup measure into flour tub or bag (flour settles = 2 cups will be more than 300g = your cookies will puff more). *I am not usually this pedantic, only when a recipe is more sensitive than usual* 2. Baking soda (bi-carb) – don’t substitute with more baking powder if you don’t have baking soda, it will make the cookies puff up into rock-cake form. You need baking soda! 3. Choc chips – Milk choc chips are considerably sweeter so I like a combination of dark and milk so it’s not overwhelmingly sweet. Feel free to use more or less of either (I realise 400g is a neat 2 x standard Australian 200g packs!) or cut your own chocolate, for larger melty pools of chocolate (I prefer the littering of smaller chips all throughout, plus it’s more convenient – and I plan to make these cookies a lot, forever!) 4. Cooled browned butter – Cool enough so it won’t melt the sugar or melt the choc chips, but not so cold the edges solidify (if it does, re-melt and cool again). 5. Smaller cookies – This recipe works great for smaller cookies too but roll them into balls instead of forming fat discs. Here are the bake times:
1 tbsp (#20 cookie scoop) – 12 to 13 minutes
2 tbsp (#40 cookie scoop) – 13 to 14 minutes
3 tbsp (~60g/2oz/#20 cookie scoop) – 14 minutes
6. Fridge chilling = flour hydration so dough doesn’t melt into a thin cookie, and flavour development = tastier, more golden, chewier and crispier edges/base, and nicer shape (ie less spreading). See post for description of what you lose with shorter chill times.
12 – 24 hrs – Recommended, for best results, exactly as you see in post, my perfect cookie.
24 – 48 hours – Also excellent, cookie is a tiny bit thicker and spreads slightly less, crispiness is slightly better.
3 – 5 days – Diminishing returns and risk of ball drying out. Better to freeze at 24 hours, than thaw on demand.
5 hours – My minimum. If I can’t do this, I make Oatmeal Browned Butter Cookies (no chill time, oats gives these instant chew whereas these need chill time).
Cookie emergencies (it happens):
No chilli time – Doesn’t work, cookie spreads way too much
1 hour minimum chill time – increase cornflour by 2 teaspoons. Cookie has less chew, less crispy, less golden colour, and faint thin crackly surface (only I notice, apparently) compared to 12hr fridge. Still an above average “need it now!” chocolate chip cookie, nobody who got these complained!
Emergency choc chip cookies, regular size, easier, no chill time here.
7. Oven temp is only 10°C different here for fan v conventional. See FAQ. 8. Bake one tray at a time for standard Australian ovens (60cm) though if you have a large one (90cm) you can bake 2 trays at the same time. 9. Decorate choc chips – lightly press in to the surface or just rest on surface (chocolate will melt and adhere). Storage – exceptional shelf life. Excellent for 2 days, still near excellent on day 3, still great days 4 and 5. Store in an airtight container in the pantry. Freezing – Uncooked dough discs can be frozen after the 12 hour fridge time. Bake from frozen per recipe (cookies are a bit thicker) but I prefer to thaw overnight in the fridge than bake per recipe (they come out exactly as pictured). See FAQ for more details and tips. Nutrition – Let’s just say it’s more than water, less than a Big Mac Meal (I hope!). Will update shortly.
I will continue to add more to this Troubleshooting section as I start seeing questions coming through from people who have made the recipe.
Troubleshooting tips
Here’s what can cause this:
Your dough discs were not the specified 3.75cm / 1.5″ thick. Don’t shortchange yourself! Flatter disc = thinner cookies.
Thin flimsy baking tray = heat retention not good = cookies spread more before the edges set so they end up thinner.
Mis-measured an ingredient. Not enough flour or too much sugar, or your eggs were jumbo (you didn’t use ostrich eggs did you?? ).
Your oven runs cold = cookies have longer to melt and spread before the edges set = thinner cookie.
Your baking powder is dead so the cookie didn’t rise at all. (Here’s how to test if your baking powder is still alive).
I bet they were still YUM though!
Here’s what can cause this:
Your dough discs were much thicker than the specified 3.75cm / 1.5″ thick!
You forgot to flatten into discs and made them balls or domes instead. These bake with more of a “hump” in the middle.
You mis-measured and used too much flour or cornflour, or forgot to pack the cup tightly when measuring the brown sugar so you didn’t use enough.
Your oven runs hot, so the edges of the cookie sets before it has time to melt sufficiently, causing it to be thicker.
I bet these were still great though! And honestly, some people aim for extra thick cookies with a big gooey centre!
That’s because you didn’t press / roll the dough together well enough when you formed the dough discs! Did you have large cracks or seams in your discs?? I bet you did! (And I speak from experience here, from those times I didn’t shape my dough discs properly and they cracked open in the oven like a crevice).
Do they have a very dark brown edge and much paler surface? If so, my first question is – DID YOU CHILL THE DOUGH?? Because dough chilling makes the cookies bake up a much more beautiful even golden brown all over (well, they are paler out of oven but they depend in colour as they cool).
Secondly, you used brown sugar, yes? This gives the cookies colour too.
And the third reason is the baking tray and evenness of heat distribution in your oven. Flimsy trays will distribute heat less evenly (ie more direct, harsher heat on the base and edge of the cookie in contact with the tray = browns faster than the rest of the cookie). And hotter ovens or ovens with patchy heat distribution will brown parts of the cookie faster than others.
Life of Dozer
The photo I chose to show you:
Though every other shot was more like this:
Because he wasn’t interested in attention. THIS is what he was after!
(And plenty of it, he got, unsurprisingly!)
PS It’s yakitori, we like doing yakitori nights for get togethers! The recipe is here on my mother’s website, RecipeTin Japan.
Make sure you use large eggs which are 50-55g / 2oz each in the shell, sold in cartons labelled “large eggs”. If you only have jumbo or XL eggs, see 
12 to 24 hours
Note: You still need to do the fridge time before freezing as all the above listed good things that happen to cookie dough in the fridge can’t happen when frozen rock solid.
Why does the colour of the cooking vessel matter? It’s easier to see when the butter changes from yellow to golden. If using a black pan, you need to rely on your smell or using a spoon to scoop the butter up to check the colour.
TIP: While still hot, you can also use a spatular to reshape wonky ones into neat circles.
). Will update shortly.
Not enough flour or too much sugar, or your eggs were jumbo (you didn’t use ostrich eggs did you?? 
).
