2 tbsp. flour
3/4 c. milk
3/4 c. butter, softened
3/4 c. sugar
1 tsp. vanilla

Combine flour and small amount of milk in saucepan. Mix until smooth. Add remaining milk, slowly stirring, until smooth. Cook over medium heat until bubbly and thickened, stirring constantly. Cool completely.

Beat butter and sugar until light and fluffy. Add cooled milk mixture and vanilla; beat until smooth and fluffy.