Does accidental science still count as an experiment? I’m going to rule yes, and go ahead and share the results of my totally unintentional study of how dough temperature affects cookie baking. In other words, I got distracted halfway through making cookies, stuck the dough in the fridge, ate a good amount of it straight from the fridge, and then finally got around to baking the rest of them.
Next to the first round of cookies, baked immediately at room temperature, the differences were striking. One large, flat, and crispy around the edges, the other taller, craggy, and fudgy all the way through. It’s exactly what you’d expect, but I forgot to expect it.
The explanation is pretty simple: it’s a race between butter melting and proteins setting. As the dough heats up, the solid fat turns to liquid and the dough softens, expanding out and flattening. But as the dough temperature rises, the egg proteins start to set, firming up the structure and preventing any more change in shape. Starting at room temperature gives the butter a head start and leads to the flatter, crispier cookies, while starting out cold means that the egg proteins set before the butter melts much and the cookies wind up smaller and fudgier.
So we actually have a practical lesson for once—chill your cookie dough for fudgier cookies. Bam! Science.