Line an 8-inch or 9-inch square baking pan with parchment paper, leaving an overhang on two sides for easy removal.
In a medium bowl, mix graham cracker crumbs, melted butter, brown sugar, and salt until the texture resembles wet sand.
Press the mixture firmly and evenly into the bottom of the prepared pan using the bottom of a measuring cup. Chill while you make the filling.
In a large mixing bowl, beat the room-temperature cream cheese with an electric mixer until completely smooth, about 2 minutes.
Add pumpkin puree, powdered sugar, vanilla, pumpkin pie spice, and cinnamon. Beat until creamy and well combined.
In a separate cold bowl, whip the heavy cream until stiff peaks form.
Gently fold the whipped cream into the pumpkin cheesecake mixture with a rubber spatula until no streaks remain.
Spread the filling evenly over the chilled crust and smooth the top with an offset spatula.
Cover and refrigerate for at least 6 hours, preferably overnight, until firm enough to slice.
Lift the bars out using the parchment paper, slice with a sharp knife, and add whipped cream or extra spice before serving.