Buttermilk Chocolate Cake with Chocolate Frosting

"This is one of my Sister's best recipes!  We've had it on many occasions over the years.  It's my all time favorite chocolate cake!!!"

Cake:
2 sticks or 1 cup butter
5 Tablespoons cocoa powder
1 cup water
2 cups flour
2 cups sugar
1 teaspoon baking soda
1/2 teaspoon salt
1 cup buttermilk
2 eggs
1 teaspoon vanilla

Preheat oven to 350 degrees.  Melt butter in a saucepan.  Add cocoa powder and water.  Bring to a boil.  Pour boiling ingredients over flour, sugar, baking soda and salt in a mixing bowl.  Add buttermilk, eggs and vanilla.  Pour into a 9x13 pan that has been sprayed with non-stick cooking spray.  Bake at 350 degrees for 35 minutes.  Allow to cool and top with frosting (Recipe follows).

Frosting:
1 stick or 1/2 cup butter
6 Tablespoons buttermilk
4 Tablespoons cocoa powder
1 pound box powdered sugar

Melt butter in a saucepan.  Add buttermilk and cocoa powder.  Bring to a boil.  Remove from the heat and add to powdered sugar.  Mix with an electric mixer until well blended.  Spread frosting on cooled cake.