Bake the cake by package directions in a large cookie sheet with sides for twenty minutes. Cool completely. Mix 1 1/4 c milk with 5 tbsp. Flour ina saucepan.Cook until thick and set aside to cool. Mix granulated sugar with shortening, vanilla, and margarine. Beat in flour and milk and beat until smooth. Spread over cake and chill in refrigerator. Melt unsweetened chocolate. Heat the evaporated milk and margarine to boiling point and when margarine is melted, add to the chocolate. Beat in powdered sugar and pour over chilled cake frosted with white substance. Chill and cut into squares.

Tastes just like the Hostess snack would if it were fresh.