Penuche Icing for Spice Cake

Melt ½ cup butter.  Add 1 cup packed brown sugar.  Boil over low heat for 2 minutes, stirring constantly.  Stir in ¼ cup milk.  Stir until it comes to a boil.  Cool to lukewarm.  Gradually add 1-3/4 to 2 cups sifted confectioner’s sugar.  Beat until spreading consistency.  If icing becomes to stiff, add a little hot water.