German Chocolate Frosting with Walnuts

2 egg whites, lightly beaten

1 (12 fluid ounce) can fat-free evaporated milk

1 ½ cups white sugar

½ cup light butter, softened

1 (7 ounce) package flaked coconut

1 cup chopped walnuts

Stir the lightly beaten egg whites, evaporated milk, sugar, and light butter together in a saucepan over medium heat until thickened and bubbly, 10 to 12 minutes.

Fold the coconut and walnuts into the thickened mixture. Set aside to cool completely before using.