Preheat the oven to 325°F. Grease an 8×8 inch baking dish and line it with parchment. You should have enough parchment to cover the bottom of the dish with an overhang on 2 sides. This will help you lift the bars out after they’ve baked. Optional tip: secure the parchment overhang with metal binder clips.

If you’re using graham cracker sheets, blitz them in a food processor until they’re fine crumbs. Alternatively, you can buy pre-made crumbs.

Mix the graham cracker crumbs with the sugar in a food processor or bowl. Mix in the melted butter until the mixture resembles coarse, wet sand.

Pour the mixture into the prepared baking dish and press down into an even layer. Bake for 8 to 10 minutes and set aside to cool.

In a medium sized bowl, mix together the pumpkin puree, sugar, pumpkin pie spice, cinnamon, and cornstarch. Gently mix in the egg yolk until just combined.

In a separate, large bowl, beat together the cream cheese and sugar with a hand mixer, then mix in the sour cream, lemon, vanilla, cornstarch and salt. Mix in the beaten eggs until just combined. Be careful not to overmix.

Gently fold ¾ cups of the cheesecake filling into the bowl with the pumpkin filling.

Assemble the cheesecake by alternating 3 to 4 tablespoon-sized scoops of regular cheesecake and pumpkin cheesecake onto the crust (you should have about 6 scoops of each mixture), until all the filling is used up. Use a knife to gently swirl the cheesecake flavors and make a marbled effect.

Tap the cheesecake against the counter a couple of times to get any bubbles out, then bake it for about 35 minutes, or until the cheesecake is mostly set with only a slight wobble in the middle.

Remove the cheesecake from the oven and let it rest on the counter until it comes to room temperature, then chill it in the refrigerator for at least 3 hours or up to overnight for best results.

Slice the cheesecake into 16 squares (or cut them even smaller for bite-sized treats) and serve.