Bloom the gelatin (optional but pro move): Sprinkle gelatin over 1 tablespoon cold water. Let it sit 5 minutes until spongy.
Warm the cream: Heat 1/3 cup cream until steaming (not boiling). Microwave 30–45 seconds or warm on the stove.
Melt the chocolate: Place chopped chocolate in a heatproof bowl. Pour hot cream over it. Let sit 1 minute, then stir until glossy and smooth. If using gelatin, melt it gently (5–10 seconds in the microwave) and whisk it into the chocolate mixture.
Flavor it: Stir in vanilla, peppermint extract (start with 1/2 teaspoon), sugar, and salt. Taste and adjust the mint and sweetness. The mixture should be slightly stronger than you want the final mousse—chilling mutes flavor.
Cool to lukewarm: Let the chocolate base sit 5–10 minutes, stirring occasionally. You want it warm, not hot, so it doesn’t deflate the cream.
Whip the cream: In a cold bowl, whip 1 cup heavy cream to soft peaks. Don’t go to stiff peaks or folding will be a nightmare.
Fold like a champ: Add one-third of the whipped cream to the chocolate base and whisk gently to lighten. Switch to a spatula and fold in the remaining cream in two additions until no streaks remain.
Fill the cups: Spoon or pipe mousse into your cups. Smooth the tops or leave them swirly if you’re going for that artisan vibe.
Chill: Cover lightly and refrigerate for at least 1–2 hours, or up to 24 hours, to set and develop flavor.
Garnish and serve: Top with whipped cream, crushed peppermint, and chocolate shavings. Serve cold. Accept compliments graciously (or don’t; your call).