Chocolate Texas Sheet Cake

Chocolate Texas Sheet Cake
1 cup butter, cubed
1 cup water
1/4 cup baking cocoa
2 cups all-purpose flour
2 cups sugar
1 tsp baking soda
1/2 tsp salt
2 eggs, lightly beaten
1/2 cup sour cream
FROSTING:
1/2 cup butter, softened
3 3/4 cups confectioner's sugar
1/4 cup baking cocoa
1 tsp vanilla extract
5 to 6 tbsp milk
In a large saucepan, bring the butter, water and cocoa just to a boil. Immediately remove from the heat. Combine the flour, sugar, baking soda and salt; stir into butter mixture. Combine the eggs and sour cream; stir into the butter mixture until blended.
Pour into a greased 15 x 10 x 1 inch baking pan.
Bake at 350 for 18-25 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.
For frosting, in a large mixing bowl, cream the butter and confectioner's sugar. Add cocoa, vanilla and enough milk to achieve desired consistency. Spread over cake.