Step 1
Begin by preheating your oven to 350ºF. Generously grease a 9-inch springform pan with baking spray.
Step 2
Prepare the brownie layer by whisking together the all-purpose flour, dark cocoa powder, baking powder, and kosher salt in a medium-sized bowl until thoroughly combined. In a large microwave-safe bowl, combine the butter and chocolate chips, heating in the microwave until melted, approximately 1½ minutes. Stir until the mixture is smooth. Incorporate the granulated and brown sugars, followed by the eggs, adding each one sequentially and whisking until fully integrated. Finally, stir in the vanilla extract and gently fold in the dry ingredients.
Step 3
Pour the brownie batter into the prepared springform pan. Bake for about 45 minutes, or until the brownie is set and a toothpick inserted comes out clean. While the brownie is still warm, use a spoon to press it down evenly to form a crust that rises halfway up the sides of the pan. Allow it to cool completely on a wire rack.
Step 4
While the brownie crust cools, prepare the cheesecake filling. Lower the oven temperature to 325ºF. In a large bowl, use a hand mixer to beat the softened cream cheese and brown sugar until the mixture is light and fluffy. Gradually add the eggs, mixing thoroughly after each addition. Then, blend in the pumpkin puree, sour cream, flour, vanilla extract, pumpkin pie spice, and kosher salt until everything is evenly incorporated.
Step 5
Wrap the bottom of the springform pan in aluminum foil to prevent leaks. Pour the cheesecake filling over the cooled brownie crust, and then place the pan into a deep roasting pan.
Step 6
Transfer the roasting pan to the oven, pouring enough boiling water into it to reach halfway up the sides of the springform pan. Bake until the center of the cheesecake exhibits a slight jiggle, approximately 55 minutes. Once done, turn off the oven, prop the door open, and allow the cheesecake to cool inside for one hour. Afterward, remove the aluminum foil and refrigerate the cheesecake in the pan until it firms up, which should take at least five hours or can be left overnight.
Step 7
Before serving, drizzle thick caramel sauce over the top, dollop the outer rim with whipped cream, and finish by sprinkling additional pumpkin pie spice for an elegant presentation.