Wow! I just thought this up and it is OUTstanding.
One half cup of quality yogurt, a tbl or perhaps less of dried cocoa powder, a bit of stevia or erythrobate.
Do not feel guilty! About 70 calories and 5 grams of carbs.
I used to do this pre-primal with hot chocolate mix and yogurt...but add a little flour and little cornstarch and you've got a brownie!