Prepare the Brownie Base

• Preheat the oven to 350°F (175°C). Line a 9-inch springform pan with parchment paper.

• Melt the dark chocolate and butter together in a heatproof bowl over simmering water or in the microwave. Stir until smooth and let cool slightly.

• Whisk in sugar, then add the eggs one at a time, mixing until fully incorporated.

• Sift in the flour, cocoa powder, and salt. Fold gently to combine.

• Pour the batter into the prepared pan and bake for 15 minutes.

Make the Cheesecake Filling

• Beat the cream cheese and sugar until smooth. Add eggs one at a time, mixing on low speed to avoid air bubbles.

• Mix in the vanilla extract, heavy cream, and cornstarch until fully combined.

Layer and Swirl

• Pour the cheesecake filling over the partially baked brownie base.

• Drop spoonfuls of reserved brownie batter onto the cheesecake and use a skewer to create swirls.

Bake in a Water Bath

• Wrap the pan in aluminum foil and place it in a larger baking dish. Fill the dish with hot water until it reaches halfway up the pan.

• Bake at 325°F (160°C) for 45–50 minutes or until the edges are set and the center is slightly jiggly.

Cool and Chill

• Allow the cheesecake to cool in the oven with the door ajar for 1 hour. Refrigerate for at least 4 hours or overnight before serving.

Decorate and Serve

• Top with whipped cream, chocolate ganache, and garnishes of your choice. Slice and serve chilled.