To make cake: Add group 2 to group 1, then add group 3. Pour into greased 10 ½ x 15 inch sheet pan. Bake at 375° for 20 minutes only. Do not overbake. After cake has baked for 15 minutes, begin icing.
To make icing: boil margarine, milk and cocoa. Then add powdered sugar and vanilla. Spread on hot cake. Optional: top with chopped nuts.