Angel Food Cake Icing

1/3 c Cornstarch
1/3 c Sugar
2 c Milk
1 Egg
1 Or 2 tsp. vanilla
1/2 lb Butter
1 c Powdered sugar
Yolk


Mix the cornstarch and sugar. Add milk and egg yolk. Cook until thick,
stirring constantly. Add vanilla. Cool until COLD. Cream the butter
and powdered sugar. Add cold custard. Beat 20 minutes.