Preheat oven to 180 C / Gas 4. Lightly grease a 23x33cm or similar sized baking dish.
In a medium saucepan over medium heat, melt butter. Stir in the sugar and mix well. Stir in digestive biscuit crumbs. Pat the mixture into baking dish.
In a medium mixing bowl, beat together the eggs, sugar and cream cheese. Pour the mixture over biscuit base.
Bake 20 minutes in the preheated oven. Remove from heat and allow the mixture to cool.
In a small bowl, dissolve the gelatine in water.
In a medium saucepan over medium heat, mix the pumpkin puree, eggs, milk, sugar, salt and cinnamon. Reserve the egg whites. Stirring constantly, cook until thick, about 4 minutes. Remove from heat and mix in the gelatine. Allow the mixture to cool for approximately 20 minutes.
In a small bowl, beat the 3 egg whites until stiff. Gently fold the egg whites into the cooled pumpkin mixture. Pour the pumpkin mixture over the cream cheese mixture. Top with whipped cream. Cover and refrigerate approximately 2 hours.