Line one 23cm quiche dish with whole ginger nut biscuits, breaking as necessary for fitting.
In a saucepan over medium heat cook pumpkin puree to heat through, stirring frequently.
Separate the eggs. Combine the egg yolks, 100g sugar, milk, spices and butter. Add to pumpkin and cook, stirring frequently until mixture is of custard consistency. Remove mixture from heat.
Soften gelatine in the cold water and stir into the pumpkin until dissolved. Chill mixture until it begins to stiffen (about 1 1/2 hours).
Whip egg whites with the remaining 100g sugar until stiff. Fold whipped egg whites into the pumpkin mixture. Spoon mixture into the prepared dish and chill until set (about 3 hours). Serve topped with whipped cream.