Preheat the oven to 350 °F Spray a 9-inch deep pie dish with cooking spray.
Place the chocolate sandwich cookies in a food processor and pulse until finely ground. Add in the melted butter and pulse until moistened. Press the mixture into the bottom and up the sides of the prepared pie dish. Bake for 10 minutes, or until fragrant and set. Let cool completely on a wire rack.
Filling
Chop the bittersweet chocolate and melt it in a microwave-safe bowl for 30-second increments, stirring between each increment or in a double boiler. Once melted, remove from the heat and let cool.
In a small saucepan, whisk together the granulated sugar and eggs. Set over medium-low heat and cook, whisking constantly, until the mixture reaches 160 °F and coats the back of a metal spoon. Remove from heat and stir in the melted chocolate and vanilla until smooth. Cool to just warm, stirring occasionally.
Using an electric mixer, beat the butter until light and fluffy, about 3 minutes. Gradually add in the cooled chocolate mixture then beat on high speed for 5 minutes, or until light and fluffy.
In a clean bowl use an electric mixer to beat the cream until it begins to thicken. Add the powdered sugar and beat until stiff peaks form. Fold the whipped cream into the chocolate mixture.
Pour the mixture into the pan, smoothing evenly. The pie will be tall with filling. Chill for 6 hours.
Topping
Use an electric mixer to beat the cream until soft peaks form. Add the vanilla and gradually the powdered sugar. Mix on high speed until stiff peaks form. Top the pie with whipped cream and garnish with chocolate shavings or dust with cocoa powder or crushed chocolate sandwich cookies.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.