Preheat oven to 325 degrees F. Spray a 9 x 13 pan with nonstick spray; set aside.
Using a whisk, mix the sugar, brown sugar, cornstarch, cinnamon, ginger and salt in a medium-sized bowl until no lumps remain.
Blend in the pumpkin, whipping cream, sour cream and eggs.
Pour the mixture into the pan and bake for 45-60 minutes or until filling has puffed at the edges and center is almost set.
Let cool completely, then move to an airtight container large enough to gently mix the filling. Store in a the refrigerator overnight.