Step 1: Prepare the Crust

1. Preheat your oven to 325°F (163°C).
2. In a medium bowl, mix graham cracker crumbs, sugar, cinnamon, and melted butter until well combined.
3. Press the mixture into the bottom of a 9-inch springform pan, ensuring an even layer.
4. Bake for 10 minutes, then set aside to cool.

Step 2: Make the Cheesecake Batter

1. In a large mixing bowl, beat cream cheese until smooth.
2. Add granulated sugar and mix until fully incorporated.
3. Stir in vanilla extract and sour cream.
4. Add eggs one at a time, mixing on low speed to avoid overbeating.

Step 3: Prepare the Pumpkin Swirl

1. In a separate bowl, whisk together pumpkin puree, brown sugar, pumpkin pie spice, cinnamon, and egg yolk.
2. Mix until smooth and fully blended.

Step 4: Create the Swirl Effect

1. Pour half of the cheesecake batter into the prepared crust.
2. Spoon dollops of the pumpkin mixture over the batter.
3. Add the remaining cheesecake batter on top.
4. Use a knife or toothpick to swirl the pumpkin mixture into the cheesecake for a marbled effect.

Step 5: Bake the Cheesecake

1. Wrap the bottom of the springform pan in aluminum foil to prevent leaks.
2. Place the pan into a larger baking dish and fill the dish with hot water halfway up the sides (water bath method).
3. Bake for 55-65 minutes, until the edges are set but the center is slightly jiggly.
4. Turn off the oven and let the cheesecake cool inside with the door slightly open for one hour.

Step 6: Chill & Serve

1. Once cooled, refrigerate for at least 4 hours (preferably overnight) to allow it to set completely.
2. Remove from the springform pan and garnish with whipped cream and cinnamon if desired.
3. Slice and serve!