- Sift dry ingredients into bowl.
- Melt margarine and mix with cocoa and water.
- Bring to a rapid boil and pour over dry ingredients.
- Add buttermilk and eggs.
- Bake in cookie sheet pan with edge at 350ºF for 15 to 20 minutes.
- ICING FOR SHEET CAKE: Melt margarine, cocoa and buttermilk.
- Bring to a boil and add powdered sugar and black walnuts.
- Spread while cake is hot.