Step 1: Preheat your oven to 325°F (165°C) and grease a 9-inch springform pan. Mix the chocolate graham cracker crumbs with melted butter and press firmly into the bottom of the pan. Bake for 10 minutes and let cool.
Step 2: In a large bowl, beat the softened cream cheese and sugar until smooth and creamy. Add vanilla extract and then add eggs one at a time, mixing on low speed until just combined.
Step 3: Divide the cheesecake batter into two equal portions in separate bowls.
Step 4: In the first bowl, fold in the pumpkin puree, cinnamon, ginger, and nutmeg until well incorporated.
Step 5: In the second bowl, gently fold in the melted bittersweet chocolate until the batter is a uniform chocolate color.
Step 6: Spoon alternating dollops of pumpkin and chocolate batter onto the prepared crust. Use a knife to gently swirl the batters to create the pumpkin chocolate swirl cheesecake marble effect.
Step 7: Wrap the bottom of the pan in foil and place it in a water bath. Bake for 65-75 minutes until the edges are set but the center still has a slight jiggle.
Step 8: Turn off the oven, crack the door, and let the cheesecake cool inside for one hour before moving it to the refrigerator to chill for at least 6 hours.