Becky, this is the recipe I use all the time.
Caramel Icing

1 stick butter
1/4 cup milk
1 cup light brown sugar (packed)
2 cups or more sifted confectioners sugar

In a sauce pan melt butter and brown sugar, being careful not to burn. Bring to a full boil for 2 minutes stirring constantly.
Add milk, bring to full boil again.
Cool just to lukewarm and add confecioners sugar and mix well...Add more milk or sugar to make spreading consistency you want.