Mom's Brown Butter Frosting

This is a delicious frosting and we always made it for the Treasure Chest Bars. This is from my mom's recipe box written on a very well worn card.

Brown 1/4 c. butter over med. heat until deep brown. Remove from heat. Blend in 2 cups sifted powdered sugar and 1/2 tsp vanilla. Add 2 T. milk. Beat until smooth.