Preheat your oven to 350°F (175°C) and line an 8-inch springform pan with parchment paper, lightly greasing the sides.

Melt the bittersweet chocolate and butter together in a heat-safe bowl over simmering water or in the microwave in 20-second bursts, stirring until smooth and glossy.

Whisk in the egg while the mixture is still warm, then add in the sugar, vanilla, and salt.

Sprinkle the flour over the mixture and mix just until no dry streaks remain. Spread batter into the prepared pan and bake for 12 minutes.

Lower the oven temperature to 300°F (150°C). Beat the cream cheese on medium speed until smooth and lump-free, then blend in the sugar.

Add the eggs one at a time on low speed, followed by the sour cream and vanilla. Gently fold in the mini chocolate chips.

Once the brownie base has cooled slightly, pour the cheesecake filling over it and smooth the top with a spatula.

Bake at 300°F (150°C) for 40 minutes, until the edges set and the center has a soft jiggle.

Turn off the oven, crack the door with a wooden spoon, and let the cheesecake cool slowly inside for 30 to 45 minutes.

Run a thin knife around the edge to loosen before letting it cool to room temperature and chilling for at least 4 hours.

Warm the heavy cream until steaming, pour it over chopped dark chocolate, let sit for a minute, and stir until smooth.

Spread the ganache over the chilled cheesecake and allow it to gently flow to the edges.