Prepare the pan. Line an 8x8-inch square baking pan with parchment paper, leaving enough overhang on the sides to easily lift the cheesecake out later.
Make the graham cracker crust. In a medium bowl, combine the graham cracker crumbs, brown sugar, cinnamon, and salt. Pour in the melted butter and stir until all of the crumbs are evenly moistened.
Press the crust into the pan. Transfer the graham cracker mixture to the prepared pan. Firmly press it into an even, compact layer using the bottom of a measuring cup or glass. Refrigerate while you prepare the filling.
Blot the pumpkin. Spread the pumpkin puree over several layers of paper towels. Place another layer of paper towels on top and gently press to remove excess moisture. Repeat with fresh paper towels as needed.
You don't need to make the pumpkin dry. We're just removing some of that excess water.
Make the cheesecake base. In a large mixing bowl, beat the softened cream cheese until completely smooth and creamy, about 1–2 minutes.
Add the pumpkin and sugar. Add the blotted pumpkin, powdered sugar, brown sugar, pumpkin pie spice, cinnamon, vanilla, and salt. Beat until completely smooth and evenly combined.
Whip the cream. In a separate bowl, beat the cold heavy whipping cream with an electric mixer until stiff peaks form.
Fold everything together. Gently fold the whipped cream into the pumpkin cream cheese mixture in two or three additions. Fold just until evenly combined, being careful not to deflate the whipped cream.
Assemble the cheesecake. Spoon the pumpkin cheesecake filling over the chilled graham cracker crust and spread it into an even layer. Smooth the top with an offset spatula.
Chill. Cover and refrigerate for at least 6 hours, but preferably overnight, until completely set.
Slice. Use the parchment paper to lift the cheesecake from the pan. Cut into 16 bars using a sharp knife, wiping the blade clean between cuts.
Finish and serve. Top each bar with whipped cream and a light dusting of cinnamon or pumpkin pie spice. Add crushed graham crackers if desired.