1/2 c. sugar
1/4 c. flour
3 c. milk
1/2 tsp. vanilla
2 tbsp. cornstarch
pinch of salt
1 egg yolk
1 tbsp. butter
1/2 c. whipped topping (optional)

Mix sugar, flour, cornstarch and salt. Add 1 cup milk. Stir until smooth. Cook over medium heat until thickened, stirring all the time. Remove from heat. Add egg and 2 cups milk that has been warmed. Put back on heat and cook 5 minutes, stirring until thick. Remove from fire and add butter and vanilla. When cool, you may add the whipped topping if desired.