In a large bowl, combine graham cracker crumbs, melted, cooled butter, brown sugar, and kosher salt. Stir until very well mixed. Pour out into the prepared baking pan, then press firmly into a flat even layer.
Transfer to the preheated oven, then bake until set. Remove from the oven, then allow to cool slightly while you make the filling.
Beat cream cheese, sugar, and vanilla extract in the bowl of a stand mixer fitted with paddle attachment until smooth and creamy. Scrape down the sides, then add large eggs. Continue beating on medium-low until fully incorporated and the mixture is fluffy.
To the remaining cheesecake batter, add canned pumpkin purée, ground cinnamon, ground ginger, ground nutmeg, and a pinch of allspice. Beat until very well mixed. Pour this on top of the plain cheesecake filling, then smooth into an even layer.
Transfer to an oven, then bake for until the filling is set, rotating the pan once halfway through cook time.
When ready, carefully use the parchment to lift the cheesecake bars out of the pan. Cut into bars, then serve immediately! I like to dollop or pipe a little homemade whipped cream on each, sprinkle with the tiniest bit of ground cinnamon.