1/2 c. flour
1 c. milk
1 c. sugar
1/2 tsp. vanilla
1 c. butter (or half butter)
Pinch of salt

Cook flour and milk until thick, stirring constantly over low heat. Cool. Mix remaining ingredients until creamy. Add first mixture to second and beat with electric mixer until smooth, 5-10 minutes. This covers a large layer cake. Stays soft indefinitely.