1/2 c. butter
1/4 c. milk
1 c. firmly packed brown sugar
1 3/4 to 2 c. sifted powdered sugar

Melt butter; add brown sugar and bring to a boil over low heat. Boil 2 minutes, stirring constantly. Add milk; return to boil, stirring constantly. Remove from heat. Cool to lukewarm. Gradually beat in powdered sugar until of spreading consistency. Enough for 9x13 inch cake.