1 c. sugar
1/3 c. flour plus 1 tbsp.
5 tbsp. cocoa
2 c. milk
1 tbsp. butter
1 tsp. vanilla
3 egg yolks

Blend sugar, flour, cocoa and milk in double boiler. Cook 20 minutes. Beat yolks, add little of chocolate mixture. Then add egg mixture to chocolate mixture. Add butter and vanilla. Cook 2 minutes. Cool and pour into baked pie shell. Chill. Add whipped cream or Cool Whip before serving.