Not having a 15x10x1 pan, I halved the recipe and used a 9x13. This was very easy to make, but I believe I must have overbaked it. The mixture was thick and almost dough-like and the finished texture was rather dry and did not make me think "brownie". However, the fact that I prefer moist/fudgy brownies might also be affecting my judgement. Well worth trying for peanut butter fans.