1 cup milk
2 tablespoon flour
1/4 teaspoon salt
1/2 cup butter
1/2 cup shortening
1 cup granulated sugar
1 teaspoon Vanilla
Make a cream sauce with flour salt and milk. Cook till thickened, stirring constantly. Cool.
Cream butter and shortening thoroughly then add cooled sauce a little at a time. Then add granulated sugar a little at a time. Add vanilla and beat till thick.