For the Crust:
24 Oreo cookies, crushed into crumbs
3 tablespoons butter, melted and cooled
For the Chocolate Cream Filling:
2½ cups half-and-half
1/3 cup granulated sugar, divided
2 tablespoons cornstarch
6 egg yolks, at room temperature
6 tablespoons unsalted butter, cold and cut into 6 pieces
6 ounces semisweet or bittersweet chocolate, finely chopped
1 ounce unsweetened chocolate, finely chopped
1 teaspoon vanilla extract
For the Whipped Cream Topping:
1½ cups heavy cream
4½ teaspoons granulated sugar
½ teaspoon vanilla extract
1. 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. Cook on a wire rack while the filling is prepared.
2. 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.
3. Off the heat, whisk in the butter 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. Press plastic wrap directly on the surface of the filling and refrigerate the pie until the filling is cold and firm, at least 4 hours or overnight.
4. Make the Whipped Cream Topping: When ready to serve, beat the cream and sugar in the chilled bowl of an electric mixer at medium speed to soft peaks; add the vanilla. Continue to beat to barely stiff peaks. Spread or pipe the whipped cream over the chilled filling and garnish with shaved chocolate, if desired. Serve immediately.