For the crust: Preheat oven to 350 degrees. Line outside of an 9-inch springform pan with an 18 by 18-inch sheet of heavy duty aluminum foil (this will prevent water from leaking into cheesecake so make sure it doesn't get any tears).
In a mixing bowl using a fork, stir together crushed cream filled chocolate wafers with melted butter until mixture is evenly moistened. Firmly press mixture into an even layer in bottom of springform pan.
Bake in preheated oven 10 minutes then remove from oven and allow to cool on a wire rack. Reduce oven temperature to 325 degrees.
For the cheesecake filling: Bring 4 quarts of water to a boil in a large pot. Meanwhile add 6 oz. white chocolate and 1/2 cup heavy cream to a medium microwave safe bowl. Heat in microwave on 50% power in 20 second increments, stirring well between intervals, until melted and smooth. Set aside to cool.
Meanwhile in a mixing bowl using an electric hand mixer whip together cream cheese and granulated sugar just until smooth. Mix in eggs one at a time then blend in peppermint extract, vanilla extract, and sour cream. Mix in melted white chocolate mixture.
Tap bowl forcefully against countertop about 30 times to release large air pockets. Add in 5 oz chopped chocolate (I didn't mix in the small chocolate shavings for a cleaner looking cheesecake) and the peppermint bits and quickly fold several times (the peppermint bits will begin to dye the batter so fold in quickly so it doesn't tint all of it pink).
Spray the sides of springform pan lightly with non-stick cooking spray then pour mixture over crust layer in pan. Set cheesecake in a large roasting pan then set pan on rack in center of oven. Carefully pour in enough boiling water around springform pan until it comes halfway up the sides of the springform pan.
Bake cheesecake edges are beginning to set but center still jiggles slightly, about 1 hour 20 - 1 hour 30 minutes. Carefully remove from oven (and roasting pan) an allow to cool on a wire rack 45 minutes then cover with plastic wrap leaving a small opening on one side for heat to escape and chill 8 hours or overnight.
For the mousse: Melt white chocolate in a small microwave safe bowl on 50% power in 20 second intervals, stirring well between intervals until melted and smooth. Set aside and let cool until lukewarm.
Meanwhile in a mixing bowl using an electric hand mixer, whip heavy cream until soft peaks form then add sugar and whip until very stiff peaks form (it should start to loose that wet sheen - unless you live in a very humid environment in may never appear slightly dry).
In a separate mixing bowl whip cream cheese until smooth then mix in melted white chocolate and peppermint extract. Fold in whipped cream. Spread into an even layer over cooled cheesecake and return to refrigerator and chill 1 1/2 hours longer.
Garnish top edges with chopped chocolate and peppermint bits, then run a knife around edges to ensure cheesecake is loosened then remove ring from springform pan and cut into slices.