Preheat your oven to 350°F (175°C). Line an 8x8 baking pan with parchment paper, leaving a little overhang on the sides so you can lift the squares out later.

In a medium bowl, stir together the graham cracker crumbs, brown sugar, and melted butter. Mix until everything looks like damp sand. Press the mixture firmly into the bottom of your pan, making sure it’s even. Bake for 10 minutes, then take it out and let it cool slightly. Reduce the oven heat to 325°F (160°C).

In a large bowl or stand mixer, beat the softened cream cheese and sugar until smooth. Add in the eggs one at a time, mixing well after each one. Stir in the sour cream and vanilla until everything looks creamy.

Scoop out half of the cheesecake batter into another bowl. Add the pumpkin puree and pumpkin pie spice to it, and stir until blended. Now you’ll have one plain cheesecake mixture and one pumpkin cheesecake mixture.

Pour half of the plain cheesecake batter over the cooled crust. Spoon dollops of the pumpkin batter on top and swirl it lightly with a butter knife. Repeat with the remaining plain and pumpkin batters, swirling again to create a marbled effect.

Place the pan in the oven and bake for 35–40 minutes. The edges should look set, and the center should have a slight jiggle when you move the pan. Don’t worry, it will firm up as it cools.

Take the pan out of the oven and let it cool to room temperature. Then cover it and place it in the fridge for at least four hours, or overnight if you can wait that long.

Once chilled, lift the squares out of the pan using the parchment paper. Slice them into neat squares with a sharp knife. Wipe the knife between cuts for clean edges.