Line an 8x8-inch square pan with parchment paper , leaving some overhang for easy removal.

In a medium bowl, combine the graham cracker crumbs, melted butter, 1 tablespoon brown sugar, and salt. Transfer to the prepared baking pan, and then use your hands to spread and firmly press the crumb mixture to the bottom of the pan.

In a stand mixer with a paddle attachment or a large bowl with a hand mixer, beat the softened cream cheese on medium speed until fluffy. Mix in the pumpkin puree, 2/3 cup brown sugar, pumpkin pie spice, and vanilla extract into the cream cheese mixture until combined.

In a separate medium bowl, use a hand mixer or whisk to whip the heavy cream until thickened and stiff peaks form. Fold the whipped cream into the pumpkin mixture and gently stir just until combined.

Pour the pumpkin cheesecake batter over the graham cracker crust. Use a spatula or the back of a spoon to smooth the top.

Cover and refrigerate overnight, or at least 8 hours so the bars have time to set. Use the edges of the parchment paper to lift the bars out of the pan, cut into squares, and serve chilled.