In a large sauce pan, combine sugar, gelatin, salt, cinnamon and nutmeg. Stir in milk, egg yolks and pumpkin. Cook over medium heat until mixture boils and gelatin dissolves. Remove from heat. Add vanilla extract. Transfer mixture to a small bowl. Chill over ice bath until mixture mounds from spoon, about 30 minutes. In small bowl, beat egg whites until soft peaks form. Fold into pumpkin mixture with whipped cream. Pour mixture into choco-walnut crust. Chill until firm (about 1 hour). Garnish with chocolate shavings, if desired.