CREAMY EGGNOG FROSTING: In a medium saucepan combine 2/3 cup granulate sugar, 3 tablespoons all purpose flour, and 1/4 teaspoon ground nutmeg. Whisk in 1 cup dairy eggnog. Cook and stir over medium heat until mixture is thickened and bubbly. Remove from heat. Gradually stir hot mixture into 2 beaten egg yolks. Return mioxture to saucepan. Bring to a gentle boil. Cook and stri for 2 minutes more. Rmove from the heat. Add 1 tablespoon rum (or, add 1 tablespoon milk or eggnog and 1/4 teaspoon rum extract). Pour mixture into a bowl. Cover the surface with clear plastic wrap. Cool to room temperature. Do not stir. In a medium mixing bowl beat 1 cup softened butter (no substitutes) with an electric mixer on medium to high speed about 30 seconds or until fluffy. Add the cooled cooked mixture, one fourth at a time, beating on low speed after each addition until smooth.