I got this recipe from here and adapted it a little. I made a box german chocolate cake and covered it with this. I had to make 2 boxes, this covered both cake pans (9X13) with PLENTY of frosting.
1.5 cup evaporated milk
1.5 cup white sugar
5 egg yolk, beaten with 1 teaspoon water
1/2 cup butter
2 teaspoon vanilla extract
1.5 cup chopped pecans
1.5 cup flaked coconut
In a large saucepan combine evaporated milk, sugar, egg yolks, margarine and vanilla. Cook over low heat, stirring constantly, until thick. Remove from heat and stir in pecans and coconut. Spread on cake while still warm
I added more coconut to get it to the desired coconutty that I wanted, and added more pecans because I figured the coconut to pecan would not be correct.