Preheat the Oven: Start by preheating your oven to 350°F (175°C).
Make the Crust: In a bowl, combine the graham cracker crumbs and melted butter, then press the mixture tightly into the bottom of a 9-inch pie dish. Bake for 10 minutes or until set. Once done, let it cool completely.
Cream the Cheese: In a separate mixing bowl, beat the softened cream cheese until it's smooth and creamy. Gradually mix in the powdered sugar and vanilla extract until well combined.
Layer the Cream Cheese Mixture: Pour the cream cheese mixture over the cooled crust and spread it evenly.
Chill the Cheesecake: Place the cheesecake in the refrigerator and chill for at least 2 hours until it becomes firm.
Make the Whipped Cream Topping: In another bowl, whip the heavy cream with cocoa powder until stiff peaks form.
Top the Cheesecake: Once the cheesecake has set, spread the whipped cream evenly over the top. Finish by garnishing with chocolate shavings and a chocolate truffle for an extra touch of indulgence.
Refrigerate Again: Return the cheesecake to the refrigerator and chill for at least one additional hour.
Serve and Enjoy: Slice up your Decadent Triple Chocolate Mousse Cake and serve it chilled for a delightful treat!