The last six ingredients are intended for the icing.

CAKE: Heat oven to 375°F. In a microwave safe bowl, boil the butter, water and cocoa. In a mixing bowl, combine the flour, sugar and salt. Pour the butter mixture over the dry ingredients and mix well.

Add the buttermilk, baking soda, eggs and vanilla. Mix well and pour into a greased jelly roll pan or large cookie sheet with deep sides. I like to use a 21 x 15 sheet pan. Bake for 18 - 20 minutes.

Immediately after removing cake from oven, begin making your icing by heating the butter, buttermilk, and cocoa in the microwave. Let it boil for about one minute.

Pour the hot mixture into a large mixing bowl and slowly add the powdered sugar. Beat until smooth and creamy and then add the vanilla.

Pour the icing over the warm cake and spread with a spatula. If desired, sprinkle with walnuts.