Wash 2 cups of fresh raspberries thoroughly, then blend them until smooth (about 30 seconds). Strain through a fine mesh sieve to extract juice, discarding seeds.

Combine 1 tablespoon of gelatin and 2 tablespoons of cold water in a saucepan. Let it sit for 5 minutes to bloom, then heat gently until dissolved (1-2 minutes). Remove from heat and cool slightly before mixing into the raspberry puree.

In a chilled mixing bowl, whip 1 cup of heavy cream on medium speed until soft peaks form (about 3-4 minutes). Add 3 tablespoons of sugar and 1 teaspoon of vanilla extract, whipping until just combined.

Gently fold the raspberry puree into the whipped cream, starting with a small amount to lighten, then incorporate the rest carefully to maintain airiness.

Spoon the mousse into serving glasses or a dish, cover with plastic wrap, and refrigerate for at least 2 hours to set.

Once set, garnish with fresh raspberries and mint leaves, and dust with powdered sugar if desired. Serve chilled.