• Set a medium size bowl and beaters in the freezer to chill while preparing the mousse.
• Add the cold water to a small microwaveable dish and sprinkle the gelatin over the top and allow the gelatin to soften for 5 minutes. 
• Heat 2-inches of water in the bottom half of a double boiler set over medium-high heat.  
• Add the pumpkin puree, egg yolks, 3/4 cup of the sugar, milk, salt, spices and vanilla to the top portion of the double boiler, whisking to combine.  Continue whisking the mixture until thickened, about 10 minutes.  Remove the bowl from the pan of hot water.  
• Place the bloomed gelatin in the microwave and zap it for 10 seconds until syrupy.  Whisk the syrupy gelatin into the hot pumpkin mixture.  
• Transfer the hot pumpkin mixture to a large mixing bowl and set the mixture aside to cool to room temperature.
• In a mixing bowl, beat the egg whites until they hold soft peaks and slowly add in the remaining 1/4 cup of sugar.  Continue beating the egg whites until they reach stiff peaks. 
• Gently fold 1/3 of the egg whites into the pumpkin mixture.  Repeat adding/folding with 1/3 portions at a time until well combined. 
• Remove the bowl and beaters from the freezer and add 1/2 cup of the heavy cream.  Beat the cream until almost-stiff peaks form, not to the stiff peak stage.
• Gently fold 1/3 of the whipped cream into the pumpkin mixture.  Add the remaining whipped cream and fold until the mixture is no longer streaked.

Assemble the Mousse:

• Pipe or spoon the mousse into 6, 8-oz. parfait or wine glasses.  Transfer the mousse to the refrigerator and chill for at least 2 hours and up to 8 hours.
• When ready to serve the pumpkin mousse whip the remaining 1/2 cup of cream to stiff peaks and pipe on top of each serving.  Garnish with a sprinkle of cinnamon if desired.