In a medium saucepan whisk whipping cream (first amount), sugar and egg yolks. Place over medium-low heat and stir until thickened to pudding consistency, about 10 minutes. Don’t boil.
In a large bowl combine pumpkin, vanilla and spices. Add cooked mixture, stir to combine and refrigerate until cold, about 45 minutes. This can be done a day in advance.
In a clean bowl of electric mixer beat whipping cream (second amount) until it holds soft peaks. Reserve about ½ cup for garnish.
Mix remaining whipped cream into the pumpkin mixture. Portion into glasses, cover and freeze if desired.
Allow frozen mousse to sit at room temperature for 30-45 minutes before serving.
Serve with a dollop of whipped cream and any additional garnish as desired.