1 cup butter (2 sticks)
1 cup water
1/4 cup unsweetened cocoa powder
2 cups granulated sugar
2 cups all-purpose flour
1/8 teaspoon salt
2 eggs, beaten
1 teaspoon baking soda
1/2 cup sour cream
1 teaspoon vanilla
Frosting, below
1/2 cup butter 
1/4 cup unsweetened cocoa powder
1/4 cup  milk 
1 box (1 pound) confectioners' sugar, sifted (4 1/4 cups sifted) 
1/2 teaspoon vanilla 

Cake: Combine 1 cup butter, water, and 1/4 cup cocoa in a saucepan over medium heat; heat until butter melts. Add sugar, flour, salt, eggs, soda, sour cream, and 1 teaspoon of vanilla; mix well.
Pour into a  sheet cake pan.
Bake at 350° for about 20 minutes, or until a toothpick inserted in the center comes out clean.
Frost while still hot. it is meant to be
Frosting: When the cake is almost finished baking, combine 1/2 cup of butter, 1/4 cup of cocoa, and milk in a saucepan; bring to a boil.
Add the confectioners' sugar and 1/2 teaspoon of vanilla mix well with electric mixer. 

Spread to cover the hot cake.