In a large mixing bowl, whip the heavy cream with the sugar until soft peaks form.
Fold the melted chocolate into the whipped cream, being careful not to deflate it.
Add the peppermint extract and gently fold until well combined.
Spoon the mousse into serving dishes and refrigerate for at least 1 hour before serving.
For a different twist, you can substitute the peppermint extract with orange extract for a chocolate-orange mousse. If you prefer a sweeter mousse, you can increase the sugar to 3 tablespoons. Garnish with chocolate shavings or crushed peppermint candies for added texture and flavor. For a dairy-free version, use coconut cream and dairy-free chocolate chips.