Rinse fresh cranberries under cold water, removing any stems or blemished berries. Combine cranberries with sugar and water in a medium saucepan. Bring to a boil, stirring occasionally, until cranberries burst, about 10 minutes. Set aside to cool.

Transfer cooled cranberry mixture to a blender. Blend until smooth, then strain through a fine mesh sieve. Allow the strained puree to cool to room temperature.

In a small bowl, sprinkle gelatin over cold water and let bloom for 5 minutes. Gently heat until dissolved and mix into cranberry puree along with vanilla extract.

In a large mixing bowl, whip heavy cream until soft peaks form, about 3-5 minutes. Avoid over-whipping.

Gently fold the cranberry mixture into the whipped cream until fully combined.

Spoon mousse into individual cups or a large bowl. Cover with plastic wrap and refrigerate for at least 4 hours.

When ready to serve, top with whipped cream and garnish with fresh cranberries or mint leaves.