1. In a small saucepan over medium-high heat on the stove, warm 1 cup of the heavy cream until beginning to steam, but before it begins to boil.
2. Place the white chocolate in a large heat-proof bowl. Once the cream has heated up, pour the cream over the white chocolate and allow it to sit for a couple of minutes before stirring into a smooth ganache. Add the remaining cup of cream as well as the peppermint extract and whisk to combine. Place the mixture in the fridge, covered, for at least 4 hours, or up to 3 days.
3. When ready to make the mousse, pour the mixture into the bowl of a stand mixer fitted with the whisk attachment, or into a bowl for use with a handheld electric mixer. Mix on high until stiff peaks begin to form.
4. Portion the mousse into individual serving glasses (I used 6). Layer and top with crushed candy canes, if desired. Place the mousse back into the fridge for 1-2 hours prior to serving. Top with additional whipped cream or candy cane just before serving (optional).

Leftover mousse can be stored in the fridge, covered for 2-3 days.