Prepare the pan. Arrange a rack in the center of an oven, then preheat to 325°F/160°C. Line an 8x8 baking pan with two sheets of overlapping, perpendicular parchment paper, leaving an overhang on all sides. Use your hands to press the parchment down into all corners, then coat with baking spray.
Make the crust. In a large bowl, combine 120g graham cracker crumbs, melted, cooled unsalted butter, 50g brown sugar, and ¼ tsp Kosher salt. Stir until very well mixed. Pour out into the prepared baking pan, then press firmly into a flat even layer.
Bake the crust. Transfer to the preheated oven, then bake for 10-12 minutes, or until set. Remove from the oven, then allow to cool slightly while you make the filling.
Make the cheesecake filling. Beat 455g cream cheese, 150g sugar, and 2 tsp vanilla extract in the bowl of a stand mixer fitted with paddle attachment until smooth and creamy, about 2 minutes. Scrape down the sides, then add 2 large eggs. Continue beating on medium-low until fully incorporated and the mixture is fluffy. Pour the cheesecake filling on top of the slightly cooled crust, then smooth into an even layer.
Add the cookie butter. Place 75g cookie butter in a microwave safe bowl then heat on high in 30-second increments, stirring between each, until smooth and melted. Drizzle or dollop the warmed cookie butter on top of the cheesecake filling. Use a knife to swirl into the batter.
Bake the cheesecake bars. Transfer to an oven, then bake for 30-40 minutes, or until the filling is set, rotating the pan once halfway through cook time.
Cool. Place the pan on a wire rack, then cool at room temperature for at least 2 hours. Cover with plastic wrap or foil, then refrigerate for at least 6 hours or up to overnight.
Slice, then serve. When ready, carefully use the parchment to lift the cheesecake bars out of the pan. Cut into 16 bars, then serve immediately!