In a medium bowl, combine crumbs, sugar, and butter. Press the mixture into the bottom and partway up the sides of a 9-inch springform pan or 9-inch deep-dish pie pan. (It may be helpful to use a measuring cup with straight sides to press and smooth the crust.) Bake for about 8-10 minutes, just until set and aromatic. Remove from oven and let crust cool on a rack.
For the cheesecake filling, beat the cream cheese (and sour cream, if adding) with the sugar until fairly smooth. Stir in the egg and vanilla. Spoon the filling into the crust.
In a medium bowl, whisk together the sugar, salt, and spices. Add the pumpkin, milk, and eggs; whisk gently until combined and smooth. Gently spoon the pumpkin mixture over the cheesecake layer, up to about 1/4 inch of the top of the crust. (If you have extra filling, you can bake it in a custard cup along with the pie, and remove it from oven when set.)
Reduce oven temperature to 350.
If using a springform pan, place it on a baking sheet lined with foil. Bake for 50-60 minutes, until it looks set but still wobbles a bit in the center when you jiggle it. Remove pie from oven, let cool to room temperature, then refrigerate until serving. Serve with lightly sweetened whipped cream flavored with a pinch of ginger and a teaspoon of vanilla.