Meanwhile, in 2-quart saucepan, melt 1/2 cup butter over medium heat. Stir in 1 cup brown sugar. Heat to boiling, stirring constantly. Stir in 1/4 cup milk. Heat to boiling; remove from heat. Cool to lukewarm, about 30 minutes. Gradually stir in powdered sugar. Spread Caramel Frosting on cookies.