1/2 cup butter
1/4 cup vegetable shortening
3/4 cup granulated sugar
1 tsp. vanilla
3 1/2 tbsp. flour
3/4 cup milk

Combine flour and milk; cook slowly, mixing constantly (as for white sauce) until thickened. Cool thoroughly.

Mix shortening, butter, sugar and vanilla. Beat until light and fluffy. Gradually add cooked flour mixture by tablespoonfuls, beating after each addition, until creamy and light as whipped cream.

This makes a lot of frosting. If you don't use all of it, it can be stored in the refrigerator or frozen for future use. It will soften up after setting at room temperature and be as nice as when it was first made.