Combine flour and sugar in a large bowl. In a saucepan, combine and bring to a boil water, margarine, shortening and cocoa. Pour over flour and sugar mixture. Add remaining ingredients. Bake in a greased 11 x 17 pan (jelly roll pan). Bake 18 to 20 minutes at 400 degrees.
Using same sauce pan you used for above, combine: 1 stick margarine one third c. sweet milk 3.5 T. cocoa Heat till margarine is melted and all ingredients are well combined.
Add 1 lb. powdered sugar, half c. chopped nuts and 1 t. vanilla. Pour over cake immediately as it comes from oven.