My daughter baked a batch of cookies tonight. While they were in the oven I was helping wash up and noticed I was washing the whip from the mixer, not the beater. I asked her about that and she swore up and down that the recipe said to whip the butter and sugar. Of course when she showed me the recipe it clearly said "beat." Each tray of cookies came out entirely differently. They ranged from more or less normal looking to one sheet that completely melted into something that looked like a giant Florentine. Oddly enough, the dough on that sheet had rested in the refrigerator for about 2 hours.
All the cookies tasted pretty decent so I don't think the measurements were off. The only thing I can imagine is that whipping the butter rather than creaming it caused the weird behavior. Does anyone have any idea what happened here chemically?