Preheat the oven to 180°C (350°F) and grease and line the bottom and sides of an 8-inch cake tin.

In a small pot, combine the unsalted butter and dark chocolate, stirring over medium heat until melted. Alternatively, use a microwave for 30 to 60 seconds.

Allow the mixture to cool slightly.

In a large mixing bowl, whisk together the eggs, granulated sugar, and soft light brown sugar for 2-3 minutes until light and fluffy.

Pour the cooled chocolate mixture into the egg mix, whisk until fully combined.

Sift in the plain flour, cocoa powder, and salt, mixing until smooth.

Reserve two spoonfuls of brownie batter and pour the rest into the prepared tin. Bake for 40-45 minutes.

Test with a toothpick should come out mostly clean with a few moist crumbs.

Allow to cool slightly, then reduce oven temperature to 170°C (325°F).

In another large bowl, mix full-fat cream cheese, granulated sugar, corn flour, and vanilla extract until well combined.

Gradually add half of the warm double cream and mix thoroughly before adding the rest.

Gently fold in the melted white chocolate.

Pour the cheesecake mixture over the brownie base.

Dollop the reserved brownie batter over the cheesecake and swirl gently for a marbled effect.

Prepare a water bath in a large roasting tray; place the cake tin inside and pour boiling water halfway up the sides.

Bake for 45-55 minutes until the edges are set but the center jiggles slightly.

Turn off the oven and leave the cheesecake in the oven with the door cracked for one hour.

Cool completely at room temperature, then refrigerate overnight.

Remove the cheesecake from the tin, decorate with whipped cream and brownie pieces if desired, slice, and serve.