Make the crust: In a bowl, combine graham cracker crumbs and melted butter. Stir until the crumbs are well coated. Press the mixture evenly into the bottom of a parchment-lined 8x8 pan. Place in the freezer while you prepare the filling.

Whip the cream: Using a hand mixer or stand mixer with a whisk attachment, beat the cold heavy cream until stiff peaks form. Set aside.

Make the filling: In a separate large bowl, beat the softened cream cheese and powdered sugar until smooth. Add pumpkin puree, pumpkin pie spice, and vanilla extract. Beat until fully combined and creamy.

Fold in whipped cream: Gently fold the whipped cream into the pumpkin cream cheese mixture using a rubber spatula until no streaks remain.

Spread the filling: Remove crust from the freezer and spread the pumpkin cheesecake mixture evenly over the crust.

Chill: Cover with plastic wrap and refrigerate for at least 6 hours, preferably overnight.

Slice & serve: Once set, slice into bars and top with whipped cream and a sprinkle of pumpkin spice if desired.