Adapted from here. Be sure to review the tips and tricks above to ensure success.
9 oz. high quality chocolate (at least 70% cocoa), chopped
1 cup minus 1 tablespoon water (see note above)
1 tablespoon coffee liqueur
2 tablespoons sugar
1/4 - 1/2 teaspoon peppermint extract
Candy cane shards, for topping (optional)
Fill a medium bowl 3/4 full with ice and water. Set a large bowl on top of the medium bowl, so the bottom of the larger bowl sits in ice water. Set aside.
Add chocolate, water, coffee liqueur and sugar to a medium saucepan. Warm over medium heat, stirring until chocolate is melted and all ingredients are combined. Add peppermint extract, stirring until combined (I added 1/4 teaspoon plus another half 1/4 teaspoon).
Pour mixture into the prepared large bowl. Whisk until the mixture thickens. You can do this by hand or with an electric hand mixer. This should only take a couple of minutes.
Divide mousse between four bowls (or jars), top with candy cane shards, and enjoy immediately.
Recipe by Kitchen Konfidence at https://www.kitchenkonfidence.com/2012/12/5-minute-chocolate-peppermint-mousse