Line an 8 or 9 inch square baking pan with two strips of parchment paper, crossing them so the ends overhang for easy lifting.

In a large bowl, whisk together the graham crumbs, brown sugar, salt, and pumpkin pie spice. Add the melted butter and stir until the crumbs are evenly moistened.

Firmly press the crust mixture into the bottom of the prepared pan using the bottom of a measuring cup or a flat glass. Set aside while preparing the filling.

In a chilled bowl, beat the heavy whipping cream on medium high speed until stiff peaks form. Place in the refrigerator until needed.

In a separate bowl, beat the cream cheese, sugar, and salt until completely smooth and fluffy. Add the vanilla, lemon juice, pumpkin puree, and pumpkin pie spice; continue beating until the mixture is smooth and well combined.

Gently fold the whipped cream into the pumpkin cheesecake mixture with a rubber spatula, turning carefully until no white streaks remain.

Transfer the filling onto the prepared crust and smooth the top evenly. Cover the pan and refrigerate for at least 8 hours or overnight. For clean slices, transfer to the freezer for 1 hour before cutting.

Use the parchment handles to lift the chilled cheesecake onto a cutting board. Trim the edges if needed, then slice into 12 bars in a 4 by 3 grid, wiping the knife clean between each cut.

In a chilled bowl, whip the heavy cream, confectioners' sugar, and vanilla to stiff peaks. Transfer to a piping bag fitted with a large star tip and pipe swirls onto each bar. Sprinkle with pumpkin pie spice and serve immediately.