Combine Pumpkin, 1 cup cream and sugar in sauce pan and simmer for 5 minutes, whisking ocasionally. Remove from heat and cool.
Whip remaining 2 cups of cream and vanilla into soft peaks. Separately whip egg whites to soft peaks. Fold both into fully cooled pumpkin mixture until completely combined.
Chill mixture until ready to serve. Serve with a ginger snap or vanilla wafer. Can be spooned or piped with pastry bag into dish. Cookie inserted into mousse and served. Yields 10-12 servings.