Preheat the oven to 200°C / 390°F. Line an 8 x 4-inch loaf pan with parchment paper, leaving an overhang for easy removal.

Whisk 66 g caster sugar, 33 g brown sugar, and 1 egg in a mixing bowl until the mixture is pale and slightly thickened.

Melt 66 g dark chocolate with 38 g butter until smooth. Let the mixture cool briefly so it is warm rather than hot.

Pour the melted chocolate-butter mixture into the egg mixture. Whisk until fully combined.

Fold 20 g all-purpose flour and 8 g cocoa powder into the brownie batter. Stop mixing as soon as no dry streaks remain.

Transfer the brownie batter into the lined loaf pan. Spread it into an even layer across the base.

Whisk 300 g cream cheese, 150 ml heavy cream, 65 g caster sugar, and 2 eggs in a clean bowl until smooth.

Whisk 120 g dark chocolate, 6 g all-purpose flour, and 4 g cocoa powder into the cheesecake mixture until uniform and smooth.

Pour the cheesecake batter gently over the brownie layer. Level the surface with a rubber spatula.

Bake for 20 min at 200°C / 390°F until the top is dark brown and the center remains noticeably jiggly.

Cool the cheesecake in the pan to room temperature. Chill before slicing for cleaner layers and a firmer texture.