1/2 c. butter
1/2 c. sugar, granulated
1/2 c. milk
2 tbsp. flour
1 tsp. vanilla

In a bowl, cream butter and sugar well. Pour milk into saucepan. Add flour and stir. Cook milk and flour mixture, stirring constantly, until it forms a ball-like thickness. (It will pull away from the sides of the pan and form a soft ball.) Cool completely. Add flour mixture gradually to creamed mixture and mix well. Add vanilla and mix well. Spread over cake.