Line your baking pan with parchment paper, leaving some overhang on the sides so you can lift the bars out easily later. This small step makes a big difference when it comes time to slice and serve.
In a medium bowl, combine the graham cracker crumbs and granulated sugar. Pour in the melted butter and stir until the mixture is evenly coated and resembles wet sand. This buttery crumb will form the foundation for your bars.
Press the crust mixture firmly and evenly into the bottom of the prepared pan. You can use the bottom of a glass or measuring cup to pack it down tightly. Place the crust in the fridge to chill while you prepare the fillings.
In another bowl, beat the softened cream cheese until smooth and creamy. Add the powdered sugar and vanilla, then beat again until fully combined. Gently fold in the whipped cream until the mixture is light and fluffy. This will be your cheesecake layer.
Spread the cheesecake mixture evenly over the chilled crust, smoothing the top with an offset spatula if you have one. Return the pan to the fridge while you prepare the pumpkin layer.
In a clean bowl, whisk together the pumpkin puree, brown sugar, and all the spices until well blended. Gently fold in the reserved whipped cream. Spread this mixture over the cheesecake layer, smoothing it out gently to avoid mixing the layers.
Cover the pan with plastic wrap and refrigerate for at least 4 hours, or until fully set. For the best texture and clean slices, chill overnight. When ready to serve, lift the bars out of the pan using the parchment overhang and cut into squares with a sharp knife.