Combine the heavy cream, vanilla and half the sugar, bring to a boil. Combine the egg yolks and remaining sugar. Add 1/3 of the hot liquid to the egg mixture, stir constantly. Add the egg yolk mixture to the remaining hot cream, stir constantly. Stir in the cinnamon, allspice, and ginger. Fold in the pumpkin puree.
Fill buttered ramekins 7/8 full, place in a water bath. [Place ramekins in a deep roasting pan and fill pan with enough water to reach halfway up sides of ramekins.] Bake in a 325 deg. F (160 deg. C) oven until just barely set, cool 30 minutes, chill overnight.
Cover the surface of each custard with 1/8-inch of sugar, set ramekins in a hotel pan [or a deep roasting pan], surround with ice.*
Caramelize sugar under the broiler or with a torch.
*Note: Setting ramekins in ice keeps the custard from becoming reheated when caramelizing the top.