In a small bowl, sprinkle gelatin over water and let it bloom for about 5-10 minutes.
In a saucepan, combine heavy cream, pumpkin puree, sugar, vanilla, cinnamon, and nutmeg. Heat gently over medium heat, stirring until sugar is dissolved and mixture is hot, but not boiling.
Remove from heat and whisk in the bloomed gelatin until completely dissolved.
Pour mixture into serving glasses or ramekins. Let them cool to room temperature, then cover and refrigerate for at least 4 hours or until set.
Serve chilled, optionally garnished with whipped cream or a sprinkle of cinnamon.