Ingredients:

  • 115 g Unsalted Butter, melted
  • 170 g Dark Chocolate (70% Cacao), finely chopped or chips
  • 150 g Granulated Sugar (for brownie base)
  • 2 Large Eggs (room temperature)
  • 1 tsp Pure Vanilla Extract (for brownie base)
  • 60 g All-Purpose Flour, sifted
  • 15 g Unsweetened Cocoa Powder (Dutch-process preferred)
  • ¼ tsp Fine Sea Salt (for brownie base)
  • 680 g Full-Fat Cream Cheese (room temperature)
  • 150 g Granulated Sugar (for cheesecake filling)
  • 3 Large Eggs (room temperature)
  • 120 g Full-Fat Sour Cream or heavy cream (room temperature)
  • 2 tsp Pure Vanilla Extract (for cheesecake filling)
  • Zest of ½ a large lemon
  • Pinch Fine Sea Salt (for cheesecake filling)

Instructions:

  1. Prep the Oven and Pan: Preheat the oven to 160°C / 325°F. Grease and line the base of a 9-inch springform pan with parchment paper. Crucially, wrap the exterior of the pan tightly in several layers of heavy-duty foil to prevent water ingress during the water bath.
  2. Melt Chocolate: Melt the butter and chopped dark chocolate together in a heatproof bowl set over simmering water (a bain-marie), or carefully in the microwave in 30-second bursts. Stir until smooth.
  3. Mix Brownie Wet Ingredients: Whisk the sugar into the chocolate mixture. Add the eggs one at a time, whisking vigorously for 30 seconds after each addition until the batter is thick and glossy. Stir in the vanilla.
  4. Mix Brownie Dry Ingredients: Gently fold the sifted flour, cocoa powder, and salt into the chocolate mixture until just combined. Avoid overmixing.
  5. Form Base: Pour approximately ¾ of the brownie batter into the prepared springform pan. Smooth the top with a spatula to create an even base. Reserve the remaining ¼ of the batter for the swirl.
  6. Whip Cream Cheese: Beat the room-temperature cream cheese and sugar in a large bowl on medium speed until completely smooth and lump-free (about 3 minutes). Scrape down the sides often.
  7. Add Dairy and Flavour: Mix in the sour cream, vanilla extract, lemon zest, and salt until just combined.
  8. Incorporate Eggs: Reduce the mixer speed to low. Add the eggs one at a time, mixing only until the yolk disappears. Stop immediately after the last egg is incorporated to prevent adding too much air.
  9. Layer the Cake: Carefully pour the cheesecake filling over the brownie base in the pan. Gently tap the pan on the counter a couple of times to release any large air bubbles.
  10. Create the Swirl: Dollop the reserved ¼ portion of the brownie batter randomly onto the surface of the cheesecake layer. Take a skewer or toothpick and gently drag it through the batters to create a marbled effect, taking care not to pierce the bottom brownie layer too deeply.
  11. Prepare Water Bath: Place the foil-wrapped springform pan inside a large roasting pan. Carefully pour boiling water into the roasting pan until the water level reaches about halfway up the sides of the springform pan.
  12. Bake: Bake for 70 to 75 minutes. The cheesecake should look mostly set but have a slight wobble in the center (about 2 inches across).
  13. Slow Cool: Turn off the oven and prop the oven door open slightly (using a wooden spoon). Let the cheesecake cool inside the oven for 1 hour. This prevents drastic temperature changes which cause cracking.
  14. Final Cool and Chill: Remove the cheesecake from the water bath and the foil. Cool completely on a wire rack at room temperature. Once cool, transfer the cheesecake (still in the pan) to the refrigerator and chill for a minimum of 4 hours, or preferably overnight, before serving.