Peanut Butter Cream Pie

Combine sugar, cornstarch, flour and salt. Add milk and cook over low heat, stirring constantly, until mixture thickens and boils. Cook 2 minutes longer. Remove from heat and stir in small amount of the hot mixture into the beaten egg yolks. Add egg yolk mixture to the remaining hot mixture and cook 1 minute longer stirring constantly. Add peanut butter and butter. Stir until well blended. Pour into a cooled, baked pie shell. Chill well before serving.