This recipe comes from my mother and I like it because it is GOOD. It's about 100 years old and has stood the test of time in our family.
Mix sugar, cocoa, flour, and salt and set aside. Separate eggs, reserving whites in a clean, fat-free chilled bowl. Mix cream and whole milk with sugar, cocoa, flour and salt and cook over medium low heat, stirring constantly, until slightly thickened. Beat egg yolks until thick. Add small amount of chocolate mixture to egg yolks and stir. Then add egg yolk mixture to chocolate mixture and cook over medium low heat until very thick. Remove from heat, add one tablespoon butter and the vanilla. Stir, and then let cool.
While this cools, make meringue for top of pie. 4 egg whites 1 cup sugar 1 teaspoon cream of tartar Mix egg whites and cream of tartar in chilled mixing bowl until foamy and then slowly add sugar until stiff (but not dry) peaks form. Pour chocolate mixture into baked pie crust, and top with meringue. Bake in 350 degree oven until meringue is just lightly browned. Cool before serving.