For the crust: Preheat your oven to 350 degrees. Line the outside of a 9-inch springform pan with an 18 by 18-inch sheet of heavy-duty aluminum foil. This will prevent water from leaking into the cheesecake, so ensure it’s secure without any tears.
In a mixing bowl, combine the crushed cream filled chocolate wafers with the melted unsalted butter using a fork until the mixture is evenly moistened. Firmly press this mixture into an even layer at the bottom of the springform pan.
Bake the crust in the preheated oven for 10 minutes, then remove it and allow it to cool on a wire rack. Meanwhile, reduce the oven temperature to 325 degrees.
For the cheesecake filling: Bring 4 quarts of water to a boil in a large pot. In the meantime, place the white chocolate and 1/2 cup heavy cream in a medium microwave-safe bowl. Heat in the microwave on 50% power in 20-second increments, stirring well between intervals, until melted and smooth. Set this aside to cool slightly.
In a mixing bowl, using an electric hand mixer, whip together the cream cheese and granulated sugar just until smooth. Mix in the eggs one at a time, then blend in the peppermint extract, vanilla extract, and sour cream. Finally, mix in the melted white chocolate mixture until everything is well combined.
To release large air pockets, tap the bowl forcefully against the countertop about 30 times. Carefully fold in the semi-sweet chocolate and the peppermint bits, doing so quickly to avoid tinting the batter pink.
Lightly spray the sides of the springform pan with non-stick cooking spray and pour the cheesecake mixture over the crust.
Set the cheesecake in a large roasting pan and place the pan on the center rack of the oven. Carefully pour enough boiling water around the springform pan until it reaches halfway up the sides of the pan. This water bath helps to create a moist baking environment.
Bake the cheesecake until the edges are set but the center still jiggles slightly, about 1 hour 20 to 1 hour 30 minutes. When done, carefully remove it from the oven and the roasting pan, then allow it to cool on a wire rack for 45 minutes.
Cover the cheesecake with plastic wrap, leaving a small opening on one side for heat to escape. Chill in the refrigerator for at least 8 hours or overnight to allow it to set completely.
For the mousse: Melt the white chocolate in a small microwave-safe bowl using 50% power in 20-second intervals, stirring until smooth. Allow it to cool until lukewarm.
In a separate mixing bowl, whip the heavy cream until soft peaks form. Then, add the granulated sugar and continue whipping until very stiff peaks form. The cream should lose its wet sheen—if it appears slightly dry, you may need to adjust based on your environment.
In another bowl, whip the cream cheese until smooth. Mix in the melted white chocolate and peppermint extract. Gently fold in the whipped cream until smooth.
Spread this mousse evenly over the cooled cheesecake and return it to the refrigerator to chill for 1 and a half hours longer.
Before serving, garnish the top edges with chopped chocolate and peppermint bits. Run a knife around the edges of the cheesecake to loosen it, then remove the ring from the springform pan and cut into slices.
