Waterproof a 9" springform pan by placing 2 18" x 18" pieces of aluminum foil on a flat surface underneath the pan so they form a + then gently fold (to make sure you don't create any holes) up the sides of the foil around the pan. Repeat.* Line bottom of springform with parchment paper and lightly grease the inside of your entire pan with nonstick cooking spray.
Preheat oven to 350°F, with the oven rack in lower third of oven. Fill a roasting pan with 1 1/2 inches water to create a water bath for your cheesecake (to prevent cracking). Place roasting pan in the oven while you prepare your cheesecake.
To make the crust:
Pour finely ground Oreos in a large bowl and stir in melted butter; mix until well combined. Pour Oreo crumbs into springform and firmly press the crumbs down on the bottom of the pan until you have an even layer.
To make the cheesecake filling:
Add the sour cream, lemon juice and vanilla and mix until well incorporated. Pour only 1 1/2 cups of this plain cheesecake on top of the uncooked Oreo crust and evenly spread to the edges. Place in the freezer while you prepare the pumpkin layer (to create more defined layers).
To make the pumpkin cheesecake layer, add pumpkin, cinnamon, cloves and nutmeg to the remaining plain cheesecake batter and mix until well blended. Pour this pumpkin cheesecake onto the plain cheesecake and carefully spread over the plain cheesecake layer.
To gently cool your cheesecake and prevent cracking, turn off your oven and crack open the oven door. Allow cheesecake to cool in oven for 60 minutes, then remove to a wire rack and gently run a hot knife along the edges of the cheesecake.
Spread whipped cream over pumpkin cheesecake and top with crushed Oreos. Melt chocolate in microwave, mixing at 30 second intervals until melted. Stir in oil and drizzle over cheesecake by placing chocolate in a Ziploc bag, and cutting off the corner.
Plain Cream Cheese Layer
Pumpkin Cream Cheese Layer