Prepare the crust: Combine the chocolate wafer crumbs and melted butter in a medium bowl. Press the mixture firmly and evenly into the bottom and up the sides of a 9-inch pie plate. Chill the crust in the freezer for 15 minutes while you prepare the filling.
Make the chocolate filling: In a large bowl, whisk together the sweetened condensed milk, cold milk, instant chocolate pudding mix, and 1 teaspoon of vanilla extract. Beat with an electric mixer on medium speed for about 2 minutes, until the mixture thickens significantly.
Pour the chocolate filling into the chilled crust and spread evenly. Cover the pie loosely with plastic wrap and refrigerate for at least 4 hours, or until firm. This step is crucial for make-ahead preparation.
Prepare the whipped cream topping: In a separate large bowl, beat the heavy whipping cream, powdered sugar, and 1 teaspoon of vanilla extract until stiff peaks form.
When ready to serve, spread or pipe the whipped cream evenly over the chilled chocolate filling.
Garnish the top with chocolate curls or holiday sprinkles for a festive look.
Slice and serve immediately after garnishing. Store leftovers covered in the refrigerator.
Notes
For an Oreo crust chocolate cream pie, you can leave the cream filling in the Oreos when crushing for a stronger chocolate flavor.
You can make this entire pie, up to the whipped cream topping, one day ahead of your holiday party. Add the topping just before serving.
If you prefer a graham cracker crust, substitute 1 1/2 cups of graham cracker crumbs for the wafer crumbs and use 1/4 cup melted butter.