Sprinkle the gelatin over the water in a small bowl. Let it stand for two minutes to soften, then microwave for 40 seconds. Stir and set aside.
In a small saucepan, warm 1 cup of the cream and the vanilla until it just begins to bubble. Stir in the pumpkin puree and cook for 3 minutes. Remove from the heat.
Add the sweeteners, spices, and bourbon to the softened gelatin, stirring to combine them thoroughly. Stir the gelatin and spices into the cooked pumpkin mixture. Cool.
Whip the remaining cream until stiff and then fold it into the cooled pumpkin mixture.
Scoop the mousse into individual serving dishes or bowls and chill for up to 6 hours.
Garnish with a dusting of additional ground nutmeg or mace before serving.
