Mix together all cake ingredient's and bake in greased & floured 9 x 13" pan at 350 degrees for 35 to 40 minutes.
Remove cake and leave in pan, while cake is hot spread 7 ounces marshmallow cream over the top of the cake, let cool.
Next step follows immediately While cake is cooling; For icing bring to boil 3 tablespoons cocoa, 1 stick margarine and 1/3 cup milk.
Remove from heat and add 1 teaspoon Vanilla and 1 box of powdered sugar, beat well and spread over cake while warm. Let cake cool completely and divide into serving pieces. Serve and enjoy.