Moms Chocolate Pie

1 (9-inch) deep dish pie crust, baked
3 egg yolks, beaten
4 tablespoons flour
1 cup sugar
3 tablespoons cocoa
1 cup milk
1/4 cup butter or margarine
1 teaspoon vanilla extract
3 egg whites
1/4 teaspoon cream of tartar
1 teaspoon vanilla extract
1/4 cup sugar

Combine egg yolks, 1 cup sugar, flour, cocoa, milk, and butter in a large saucepan. Mix well and cook over medium heat until thickened, stirring constantly. Stir in vanilla; pour into baked pie crust.

Preheat oven to 350 degrees.

Place egg whites in medium bowl of electric mixer. Beat until frothy. Add cream of tartar and vanilla. Gradually add sugar, beating until stiff peaks form. Spread over pie filling.

Bake for 15 minutes. Remove from oven and cool on wire rack. Yield: 1 (9-inch) pie.