The first time, the cookie was perfect - great texture, great taste, and amazing gooey pockets of chocolate. It looked exactly like the recipe. The second time, though, it was a disaster. They were totally flat and had spread a lot. They were also super, super greasy, and made my belly hurt. The third attempt had basically the same issues, just not as extreme. They had spread a bit too much, and were more flat and dark around the edges.
Something I noticed while making the cookies was that my ice cream scoop was able to push out the dough from the first batch quite easily without deforming it. The next two batches, though, didn't quite like the scoop pushing them out. I managed still using it for the second batch, but I decided to form the dough from the third batch with my hands. The scoop I have is made of plastic with a lever that basically pushes the cookie dough (or ice cream) out.
The only thing I did different from the recipe was the brown sugar - there's no such thing as brown sugar where I live, so I added 2 tablespoons of molasses in addition to the 220+100 grams of sugar, all three times.
Another thing to mention is that I've been having some problems with my oven recently. It's really only about half an year old, and I've been having problems ever since I've got it. In the beginning, its temperature seemed off, but I think it's fine now. Then later, a small part of the grey coating on the bottom heating wore off, giving way to the silver metal below. Recently, it's time dial stopped ticking and moving back to zero, and a recent batch of peanut butter cookies I made had a clear gradient of less browned on the left side and more browned on the right side.
One thing that makes all this really confusing is that my first batch, even though I made them all exactly the same way, was perfect. I don't understand why the dough would be any different at all the next two times - so why was it?
3rd March, 2023:
After many times having the oven repaired but finding no difference, I lost hope in the bad oven idea.
But on a hunch, I bought a good oven thermometer, and turns out my oven was 70℃ too hot! The problem was the oven after all.