1 cup milk
4 tablespoons flour
1/2 cup margarine
1/2 cup shortening (Crisco)
1 cup confectioners sugar' sugar
2 teaspoons vanilla extract
Combine milk and flour in a small saucepan (use a whisk). Heat and stir until thick and SMOOTH. Cool.
In a large bowl, using an electric mixer, beat shortening and margarine well then add sugar and vanilla extract, beating until fluffy, 4 minutes. Continue beating while adding flour mixture (any lumps, removed). Beat until fluffy, 4 minutes or more.
Double recipe for a large layer cake.
NOTE: This looks just like a bakery frosting, but isn't as sweet!