My favorite frosting for cinnamon rolls, or coconut chew bars, or pumpkin bars.
Heat ½ stick butter in pan only until golden brown in color (stirring all the while). Quickly add about two Tbsp. milk to stop the browning, and then some SIFTED powdered sugar till you have the amount and consistency of frosting you need. It may be necessary to add tiny amounts of more milk to get a smooth texture. I drizzle this over the bars. (You have to get this onto the bars quickly before it thickens.)