Prepare the Crust

1. Make the Crust: In a medium bowl, combine the graham cracker crumbs, sugar, and melted butter. Stir until the mixture is well combined and the crumbs are evenly coated with butter.
2. Form the Crust: Press the mixture firmly into the bottom and sides of a 9-inch pie dish to form an even crust. Use the back of a spoon or your fingers to pack it in tightly.
3. Chill the Crust: Place the crust in the fridge for about 30 minutes to set while you prepare the filling.

Make the Chocolate Mousse Filling

1. Melt the Chocolate: In a heatproof bowl, melt the semi-sweet chocolate. You can do this in the microwave in 20-second intervals, stirring between each, or use a double boiler over simmering water. Once melted, let the chocolate cool slightly.
2. Whip the Cream: In a separate large bowl, beat 1 cup of heavy cream with powdered sugar and vanilla extract until soft peaks form. This will be your whipped cream base for the mousse.
3. Combine the Chocolate and Cream: Once the melted chocolate has cooled slightly, fold it gently into the whipped cream, being careful not to deflate the cream. You want the mousse to be light and airy.

Assemble the Pie

1. Layer the Mousse: Spread the chocolate mousse evenly over the prepared graham cracker crust, smoothing the top with a spatula.
2. Chill: Place the pie in the fridge for at least 3-4 hours, or until the mousse is fully set. This allows the flavors to meld together and gives the pie its perfect texture.

Prepare the Whipped Cream Topping

1. Make the Whipped Cream: Beat the remaining 1 cup of heavy cream with powdered sugar and vanilla extract until stiff peaks form.
2. Top the Pie: Once the mousse has set, spread the whipped cream over the top of the pie. You can swirl it or spread it evenly, depending on your preference.
3. Garnish: If desired, garnish the pie with chocolate shavings, cocoa powder, or even a few extra crushed graham crackers for a fun texture.