Prepare the crust: Combine graham cracker crumbs, sugar, and melted butter. Press into a pie dish and bake at 350°F (175°C) for 8–10 minutes. Let cool completely.
Make the chocolate filling: In a saucepan, whisk together sugar, cornstarch, salt, and milk over medium heat. Stir constantly until thickened. Slowly whisk a bit of the hot mixture into egg yolks, then pour them back into the pan. Cook 1–2 minutes more, stirring constantly.
Add chocolate & flavoring: Remove from heat and stir in chocolate, butter, and vanilla until smooth and glossy.
Assemble: Pour the filling into the cooled crust. Cover with plastic wrap (press it directly on the surface to prevent a skin). Refrigerate for at least 4 hours or until set.
Whipped topping: Beat heavy cream, powdered sugar, and vanilla until soft peaks form. Spread over chilled pie. Garnish with chocolate curls if desired.
