I found this on Fix-It and Forget It. I have not made it, but I am going to since it seems so easy!
1 3/4 cup brown sugar
2 cups flour
1/4 cup plus 3 tbsp cocoa powder (divided)
2 tsp baking powder
1 tsp salt
1 cup milk
1/2 stick butter melted
1 tsp vanilla
3 1/2 cups boiling water
Spray crock pot w cooking spray. Mix 1 cup brown sugar, flour and 3 tbsp cocoa, baking powder, salt, vanilla, milk and butter in bowl. Pour in crock pot. Mix remaining sugar and cocoa powder. Sprinkle over mixture. Pour in boiling water. Don't mix. Cook in high 1 1/2 hr. Let cool 10mins. Invert onto platter. Serve w cool whip, pudding or ice cream.