How to Make It
Preheat the oven to 350°. In a medium bowl, whisk the pumpkin puree with the granulated sugar, brown sugar, cinnamon, ginger, nutmeg, allspice, cocoa powder and salt. Whisk in the eggs, cream, molasses and vanilla. Pour the custard into the Prebaked Pie Pastry, spreading it evenly. Bake for 35 to 40 minutes, or until the surface is puffed, the edges are firm and the center is slightly shaky. Transfer to a rack and let cool completely.
In a small cup, sprinkle the gelatin over the cold water. In a medium saucepan, combine the pumpkin puree, brown sugar, cinnamon, ginger, nutmeg and salt. Put the egg whites in a clean medium bowl and cover with plastic wrap. Stir the egg yolks into the pumpkin mixture and bring just to a boil over moderately high heat, stirring gently. Whisk in the dissolved gelatin and the vanilla. Transfer to a bowl and let cool to room temperature.
In a medium bowl, beat the heavy cream with the 1 1/2 tablespoons of granulated sugar until soft peaks form.
Whisk the remaining 1/3 cup of granulated sugar into the egg whites. Set the bowl over a saucepan with 1 inch of simmering water; using an electric mixer, beat the whites at low speed until warm to the touch. Remove from the heat and continue beating at high speed until the whites are glossy and hold semifirm peaks.
Fold the meringue into the pumpkin mixture just until incorporated. fold in the whipped cream. Spoon the chiffon over the pumpkin pie and refrigerate until set, at least 1 hour and up to 6 hours.