1 cup butter
1 cup water
4 Tbl cocoa
2 cups flour
2 cups sugar
1 tsp baking soda
1/2 tsp salt
1 cup buttermilk or sour cream
2 eggs

bring water, butter and cocoa to a boil over medium heat and let cool. Mix remaining dry ingredients, add wet ones and mix. Pour in a greased 15 by 17 inch pan (a jelly roll pan, needs to be at least 1 inch deep). Bake at 350 for 20 minutes.

Frosting

1 stick butter
6 TBL milk
4 Tbl cocoa
1 1lb box powdered sugar
1 tsp vanilla
pinch of salt

Bring milk cocoa and butter to a boil, add sugar, vanilla and salt. Pour over warm cake.

If you don't have the right size pan, don't sweat it. You can use a smaller one, not smaller than 9 by 13, and adjust the cooking time a little. I think it tastes better in the large pan.