1In medium saucepan, combine sugar, flour, cornstarch and salt and whisk to combine. In a medium bowl, whisk milk and egg yolks until smooth. Gradually stir into sugar mixture. Cook over medium heat, stirring constantly, until mixture thickens and comes to a full boil. Boil and stir for one minute.
2Remove from heat and stir in chocolate, butter, and vanilla. Stir until melted.
3Pour into pie shell. Place plastic wrap over filling to prevent skin from forming and chill for several hours. Top with meringue or whipped cream and chocolate curls if so desired.
Footnotes
Editor's Note:
To top this pie with meringue, make the Unbaked Meringue recipe. Spread the meringue over the still-warm chocolate filling. You can either chill the pie, keeping the meringue white, or you may bake in a 400 degrees F (200 degrees C) oven until the peaks of the meringue start to turn brown, about 5 minutes. Allow pie to cool completely; chill before serving.