01 - In a medium bowl, combine graham cracker or chocolate cookie crumbs with sugar. Stir in melted butter until evenly moistened. Press firmly into the bottom and up the sides of a 9-inch pie dish. Freeze for 15 minutes to set.
02 - Preheat oven to 350°F. Bake the chilled crust for 10 minutes until set. Allow to cool completely before filling.
03 - Place chopped chocolate in a heatproof bowl set over a saucepan of barely simmering water, creating a double boiler. Stir continuously until completely smooth and melted. Remove from heat and let cool to room temperature.
04 - In a large bowl, beat unsalted butter and powdered sugar with an electric mixer on medium speed until light and fluffy, approximately 2-3 minutes.
05 - Add the cooled melted chocolate and vanilla extract to the butter mixture. Beat on medium speed until completely incorporated and smooth.
06 - Add eggs one at a time, beating on medium-high speed for 3-5 minutes after each addition. This extended mixing time is critical for achieving the signature silky, mousse-like texture.
07 - Spread the chocolate filling evenly into the cooled pie crust. Smooth the surface with a spatula. Refrigerate for at least 4 hours or until completely set.
08 - Just before serving, whip the cold heavy cream, powdered sugar, and vanilla extract together until soft peaks form. Spread or pipe generously over the chilled pie surface.
09 - Garnish with chocolate shavings if desired. Slice the pie while cold and serve immediately.