Preheat your oven to 325°F (163°C). Line a 9×9-inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.​

In a mixing bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until the crumbs are evenly moistened.

Press the mixture firmly into the bottom of the prepared pan. Bake for 8 minutes, then remove from the oven and let it cool slightly.​

In a large bowl, beat the softened cream cheese and granulated sugar until smooth and creamy. Add the eggs one at a time, beating well after each addition.

Mix in the vanilla extract and sour cream until fully incorporated. Pour the cheesecake filling over the cooled crust, spreading it evenly.​

In another bowl, combine the mashed sweet potato, brown sugar, egg, cinnamon, nutmeg, allspice, and heavy cream. Mix until smooth.

Drop spoonfuls of the sweet potato mixture over the cheesecake layer. Use a knife or skewer to gently swirl the two mixtures together, creating a marbled effect.​

Bake the bars in the preheated oven for 40-45 minutes, or until the center is set and the edges are lightly golden. Remove from the oven and let them cool to room temperature.​

Once cooled, refrigerate the bars for at least 4 hours, preferably overnight, to allow them to set completely.​

Use the parchment overhang to lift the bars from the pan. Cut into 16 squares and serve chilled.​