Make the Oreo crust:

1. Preheat the oven to 350°F.
2. Add the Oreos to a food processor and grind until finely ground. Add the melted butter and pulse until well combined.
3. Press the crumbs into the bottom and up the sides of a 9-inch pie dish, using a measuring cup to compact them. Bake for 12 minutes. If the crust comes out slightly puffed, press it down again with the measuring cup while it's still hot.
4. Let the crust cool to room temperature.

Make the chocolate filling:

1. In a medium pot, whisk together the egg yolks, cornstarch, milk, cream, and sugar until very smooth. Place over medium heat and cook, stirring constantly. When the mixture begins to steam and thicken slightly, reduce the heat to medium-low and keep stirring constantly.
2. When the mixture thickens like hot pudding and starts to bubble (you will have to stop whisking briefly to see the bubbles), cook for 1 more minute, then remove from the heat immediately.
3. Immediately add the butter, chocolate, vanilla, and salt. Whisk until the butter and chocolate are fully melted and the filling is smooth.
4. Pour the hot filling over the cooled crust. Cover lightly with plastic wrap and refrigerate for at least 8 hours, or preferably overnight.

Whip the cream and serve:

1. When the filling is cold and set, whip the heavy cream, confectioners sugar, and vanilla with a whisk or electric hand mixer until medium-stiff peaks form.
2. Dollop the whipped cream over the pie and sprinkle with the chocolate garnish before serving.