For the cake:
1 cup butter
1 cup water
1/3 cup cocoa powder
2 cups granulated sugar
2 cups all purpose flour
dash of salt
2 eggs
1 teaspoon baking soda
1/2 cup sour cream
1 teaspoon vanilla extract
for the Icing-
1/2 cup butter
1/3 cup cocoa powder
1/3 cup milk
1 box confectioners sugar (4 1/2 cups) sifted
1 teaspoon vanilla extract

1 cup butter 1 cup water 1/3 cup cocoa powder 2 cup s granulated sugar 2 cup s all purpose flour 2 eggs 1 teaspoon baking soda 1/2 cup sour cream 1 teaspoon vanilla extract 1/2 cup butter 1/3 cup cocoa powder 1/3 cup milk 1 box confectioners sugar (4 1/2 cups) sifted 1 teaspoon vanilla extract

Preheat oven to 350 degrees. Grease a 15 x 10 x 1 inch Jelly Roll pan, set aside. Sift together flour, baking soda and salt. In a medium saucepan Combine butter, water and cocoa. Heat until butter is melted. Remove from heat, add in sugar, eggs, sour cream and vanilla, blending well. Carefully whisk in flour a little at a time, making sure there are no lumps or flour pockets. Pour batter into jelly roll pan, spreading batter to all sides and corners. Bake for 20 minutes or until toothpick comes out clean. Remove from oven and frost immediately. Let cool completely before serving.
While cake is baking, make the Icing.
Combine butter, cocoa and milk in medium saucepan, bring to a boil. Remove from heat and add in vanilla and powdered sugar. Mix well, using a hand mixer is easiest. Spread over hot cake.