01 -
Preheat oven to 325°F. Line a 9-inch springform pan with parchment on the bottom and lightly grease the sides for easy release.
02 -
Melt butter until completely liquefied. Whisk in granulated sugar until smooth and glossy. Add eggs one at a time, whisking thoroughly after each. Stir in vanilla extract. Sift cocoa powder, flour, salt, and baking powder together and gently fold into the wet mixture. Stir in chocolate chips.
03 -
Spread the brownie batter evenly into the prepared springform pan. Bake for 18 to 22 minutes, until set but slightly soft. Allow to cool while preparing the cheesecake filling.
04 -
Beat softened cream cheese until completely smooth. Add sugar and beat until creamy. Blend in sour cream and heavy cream. Incorporate eggs one at a time on low speed. Add cornstarch, vanilla extract, and a pinch of salt, mixing until just combined.
05 -
Pour the cheesecake batter over the cooled brownie base. Tap the pan gently to remove air bubbles.
06 -
Double wrap the outside of the springform pan with foil. Set the pan into a larger roasting pan. Pour hot water into the roasting pan so it reaches halfway up the sides of the springform pan.
07 -
Bake at 325°F for 60 to 75 minutes until the edges are set and the center jiggles slightly with a matte surface. Turn off the oven, crack the door, and let the cheesecake cool inside for 1 hour.
08 -
Refrigerate the cheesecake for at least 6 hours or overnight to set and develop flavor.
09 -
Heat heavy cream until steaming. Pour over chopped chocolate and let sit for 2 minutes. Stir until smooth, then blend in butter, sugar, vanilla, and salt until glossy and thick. Allow to cool slightly before use.
10 -
Remove chilled cheesecake from the pan. Pour warm hot fudge sauce over the surface, allowing some to drip along the edges. Pipe whipped cream around the perimeter and add sundae toppings such as maraschino cherries, chocolate shavings, nuts, and caramel drizzle as desired.