In a food processor, pulse the ginger cookies until they are a crumble. Place in a bowl, add the melted butter and toss together. Set aside.
In a large bowl, whip the cream to soft peaks. Add ¼ cup powdered sugar, vanilla, pumpkin pie spice and the mascarpone. Whip until all incorporated then gently fold in pumpkin puree. Place in a large pastry bag with or without a tip. If you don’t have a tip - cut the end of a ziplock bag and pipe.
To assemble the mousse cups, spoon 1-2 tablespoons of the ginger crumbs into the bottom of 4-6 glasses or dessert dishes. Then pipe the filling to half full, add more ginger crumbs, pipe filling to the top and finish with ginger crumbs and some freshly grated nutmeg if desired. Serve immediately or refrigerate until needed. This is a great make ahead dessert for the holidays.