In small saucepan, melt butter. Remove from heat and whisk in cocoa powder until smooth. Transfer to large bowl. With electric mixer, alternately add confectioners? sugar and milk until icing is smooth. If icing is dry, add additional milk, 1 tablespoon at a time. If caramel has thickened, warm slightly over low heat, stirring constantly, until it thins. Add warm caramel to icing and beat until combined.