A sweet and easy pumpkin treat to bring in pumpkin season!
In a big skillet, melt the butter, then stir in the marshmallows, milk, and pumpkin. Keep stirring until everything is melted and smooth. Take the skillet off the heat and stir in the vanilla and pumpkin pie spice. Let the skillet cool completely, about 30 minutes.
In a large bowl, combine the confectioners' sugar and heavy cream. Beat that stuff with an electric mixer until stiff peaks form. Fold the newly-made whipped cream into the cooled pumpkin mixture to make the mousse. Pour the mousse into ramekins or chocolate shells. Put a cover over them and leave them in the fridge until they firm up, about 2 hours.