Preheat oven to 350 degrees F and place the oven rack in the center of the oven. Butter (or spray with a non stick spray) an 8 inch spring form pan.

For Crust: In a medium sized bowl combine the graham cracker crumbs, finely ground ginger snap cookies, sugar, and melted butter. Press the mixture onto the bottom of the prepared spring form pan. Cover and refrigerate while you make the cheesecake filling.

For Cheesecake: In a separate bowl, stir to combine the sugar, cinnamon, ginger, cloves, nutmeg, and salt.

In the bowl of your electric mixer (or with a hand mixer), on low speed, beat the cream cheese until smooth (about 2 minutes). Gradually add the sugar mixture and beat until creamy and smooth (1 to 2 minutes). Add the eggs, one at a time, beating well (about 30 seconds) after each addition. Scrape down the sides of the bowl and beat in the vanilla extract and pumpkin puree.

Pour the filling over the chilled ginger crust and place the spring form pan on a baking sheet to catch any drips. Place a cake pan, filled halfway with hot water, on the bottom shelf of your oven to moisten the air. Bake the cheesecake for 30 minutes and then reduce the oven temperature to 325 degrees C (165 degrees C) and continue to bake the cheesecake for another 10 - 20 minutes, or until the edges of the cheesecake are puffed but the center is still wet and jiggles when you gently shake the pan.

Meanwhile whisk together the sour cream, vanilla extract and sugar. Pour the sour cream mixture over the top of the baked cheesecake and rotate the pan slightly to evenly distribute the topping. Return the cheesecake to the oven and bake about 8 minutes to set the topping. Remove from oven and place on a wire rack to cool. Loosen the cake from the pan by running a sharp knife around the inside edge (this will help prevent the cake from cracking). Then place a piece of aluminum foil over the top of the pan so the cheesecake will cool slowly. When completely cooled, cover and refrigerate at least eight hours, preferably overnight, before serving.