Usually cookies need baking soda, not baking powder. If they call for both, it's at least 2x baking soda. People mix it up and add baking powder instead of soda.
Or if the cookie requires levening from the powder and it's expired, it will not rise and spread.
Soda helps with browning and powder is for levening
If you’re sure you used butter at the correct temperature, you may have accidentally ‘warmed’ your butter by mixing it with an electric mixer for too long.
Many cookie recipes start by creaming together the butter and sugar – this is just to combine the ingredients.
If you do this for too long, your room temperature butter will get super warm – and then you’ll face problem 1. all over again.
Some recipes depend on the dough being mixed just until the ingredients are combined, and not any longer. Other commenters are saying that overmixing cookies can warm the butter too much. With some recipes, like muffins, mixing creates gluten chains that lead to chewey-ness and toughness. So in order to avoid that you stop mixing asap.
Baking is a chemical reaction and the quantities, order, and methods really do have a huge impact on the result!
It's not a requirement i think, but it will shape up well and easier. You mentioned that only 1/4 did this, maybe it's due to uneven mixing? Did you use mixer for it or did you mix by hand? Maybe the butter isn't soft enough so it didn't mix well?
I think it's maybe a little but of both of what you and Annoyed_[Crabemoji] said. From what I remember of baking, butter being not chilled enough will cause it to be too soft and cook out before the chemistry can happen and they deflate like that. But obviously, it's real tough to mix in chilled solid butter, so by the time you've needed it enough for it to incorporate, it's warm again. When I was in culinary school back in the day we'd bake in huge batches, obviously, so we'd use big ole mixers to combine the cold butter quickly with giant mechanical paddles that forced it to combine while still cold. But at home, if you have to mix by hand and you know that the butter isn't cold anymore you can definitely chill the cough before baking. I don't remember much from those days (I was never a baker, I was a line cook, but baking classes were required), but when I saw your picture my immediate thought from the dredges of 20 year old memories was "That butter wasn't chilled."
Everyone is telling you too much butter, but if this only happened to part of your batch, it's more likely you didn't scrape the sides of your bowl while mixing.
When mixing anything with creamed butter, especially, you need to mix about a third of the time, scrape all the sides and fold the dough, mix, scrape, mix, and do a final scrape/ mix/ fold by hand to make sure all the butter is incorporated.
Stand mixers have this problem more than hand mixers.
This is the right answer, when using a stand mixer you want to keep the speed level low (after creaming the butter/sugar/milk) and scraping the sides down to ensure an even distribution of wets/drys. Chilling can help with maintaining a shape, but it's by no means mandatory. How did they taste? 😁
This is what I thought as well. Creaming butter and sugar properly gives the cookie better structure and spread less.
The butter also needs to be the right temperature before baking—chilling dough is sometimes needed. Also regularly scrapping the sides of the bowl while mixing is important to have a nice homogeneous cookie without gobs of dry flour or butter.
It might be too much butter, but I think you're also light on flour. If you're using cups, make sure you scoop it a little over-full and then level it off. You can also try measuring if you have a kitchen scale.
See how the bottoms of the cookies are darker than the tops? With a single pan, the pan heats up quickly and cooks the bottoms of the cookies faster than the tops (because metal is a better conductor of heat than air). With double-panning, this effect is lessened.