Make the Crust: Preheat oven to 350 degrees F. Combine the Oreo cookie crumbs and the melted butter in a medium bowl and toss with a fork until the crumbs are evenly moistened. Transfer the crumbs to a 9-inch pie plate. Press the crumbs evenly into the bottom and up the sides of the pan, forming a crust. Refrigerate the lined pie plate for 20 minutes. Bake for 10 minutes, until the crust is fragrant and set. Cool on a wire rack while the filling is prepared.
Make the Chocolate Cream Filling: Bring the half-and-half, salt and 3 tablespoons of the sugar to a simmer in a medium saucepan over medium-high heat, stirring occasionally with a wooden spoon to dissolve the sugar. Stir together the remaining sugar and cornstarch in a small bowl. Whisk the yolks thoroughly in a medium bowl for about 30 seconds, until slightly thickened. Add the cornstarch mixture and whisk until the mixture is glossy and the sugar has begun to dissolve, about 1 minute. When the half-and-half reaches a full simmer, drizzle about ½ cup hot half-and-half over the yolks, whisking constantly to temper; then whisk the egg yolk mixture into the simmering half-and-half. Return to a simmer, whisking constantly, until 3 or 4 bubbles burst on the surface and mixture is thickened and glossy, about 15 seconds longer.
Off the heat, whisk in the butter, one piece at a time, until incorporated; add the chopped chocolate and whisk until melted, scraping the bottom of the pan with a rubber spatula to fully incorporate. Stir in the vanilla, then immediately pour the filling through a fine-mesh sieve set over a bowl. Using a spatula, scrape the strained filling into the baked and cooled crust and spread into an even layer. Press plastic wrap directly on the surface of the filling and refrigerate the pie until the filling is cold and firm, about 3 hours.
Make the Whipped Cream Topping: When ready to serve, beat the cream, sugar, and vanilla on medium speed and whip. The cream will start to get frothy, and then will begin to thicken (around the 2-3 minute mark). Increase the speed to medium-high and beat for another 30 seconds to 1 minute, or until the cream looks billowy and there are distinct trails left by the whisk in the whipped cream. If you remove the whisk from the mixer and turn it upside down, the whipped cream should remain upright and not droop off. Spread or pipe the whipped cream over the chilled filling and serve. Leftovers should be stored, covered, in the refrigerator for up to 2 days.
Half-and-Half: This is a common dairy product in the United States; if you can't get it where you are, substitute equal parts heavy cream and whole milk.
Crushing Oreo Cookies: To crush the Oreo cookies, you can use a food processor to grind them into fine crumbs, or you can put them in a resealable ziploc bag and crush them with a rolling pin.
No-Bake Crust Option: If you prefer to not bake the crust, you don't have to; simply place it in the freezer while you prepare the filling. A baked crust will be firmer, while the chilled-only crust will crumble a little more when you slice into it.
Leftover Egg Whites: While I love homemade whipped cream for this pie, you may want to use leftover egg whites to create a meringue topping. Refer to my how to make meringue guide for instructions. You can also save them for omelets, meringue cookies, or pavlova.
Garnish: I love seeing chocolate curls on the top of the pie; you can also use smaller chocolate shavings, a sprinkle of cocoa powder, more crushed Oreo cookies, or nothing at all!
Make-Ahead: This pie can be made (without the topping) up to 1 day in advance. Add the whipped cream topping and garnish within a few hours of serving.
Storing: Leftovers can be kept in the refrigerator, covered, for up to 2 days.
Freezing Instructions: Chill the pie filling as instructed, then wrap the pie tightly in a double layer of plastic wrap, place the pie in a freezer-safe bag, and freeze for up to 2 months. Thaw in the refrigerator overnight, then top with whipped cream and garnish before serving.