1/2 c. butter
1 c. brown sugar
2 c. sifted confectioners' sugar
1/2 tsp. vanilla

Combine butter and brown sugar. Melt over medium heat, stir to blend. Boil 2 minutes. Cool to lukewarm. Gradually add powdered sugar. Beat until smooth and thick. Add vanilla. If too thick, add a small amount of milk or water.