Old-Fashioned Chocolate Pie

Ingredients:

1 pre-baked pie crust

1/4 cup butter

1 cup sugar

1/4 cup flour

1/4 cup cocoa powder

2 cups milk

3 egg yolks

1 tsp vanilla extract

3 egg whites

1/4 tsp cream of tartar

1/2 cup sugar

Directions:

Preheat the oven to 350°F (175°C).