The original version of this recipe was originally from the Better Homes and Gardens New Cook Book (published around 1962). I've altered it to use sweetened condensed milk (since I usually have that on hand and not evaporated) and swapped the pecans for hazelnuts.
This recipe makes enough frosting for one 13X9X2" rectangular or two 9" round cakes.
14 ounce can sweetened condensed milk (or one can evaporated milk and 1
1/3 cups sugar)
1/2 cup butter
2 eggs, slightly beaten
2 teaspoons vanilla
2 2/3 cups flaked coconut
1 cup chopped hazelnuts (or pecans)
In a heavy saucepan or double boiler, combine milk, butter, and eggs. Cook over medium low heat, stirring constantly, until bubbling and thickened; about 12 minutes. Cool slightly. Blend in vanilla, coconut, and nuts. Cool to room temperature before using.