Chocolate Pie Filling

Beat egg yolks and set aside. Reserve whites for meringue. Blend sugar, flour, cocoa and salt together. Scald milk over medium heat, remove from burner and slowly add cocoa mixture, whisking with a fork to blend. Return mixture to burner and bring to a boil over medium heat, stirring constantly. Mix a small amount of this chocolate mixture into beaten egg yolks. Stir quickly to prevent lumps. Add egg yolk mixture back into chocolate mixture and mix quickly. Bring to a boil again over medium heat, stirring constantly. Cook until mixture becomes as thick as custand. Remove from heat, add butter and vanilla. Pour into baked pie shell and top with meringue. Note: 4 level Tbsp cornstarch can be substituted for flour.