Step 1

Preheat oven to 350°F. Line a 9x9-inch or 8x8-inch baking pan with parchment paper leaving a 2-inch overhang along each side.

Step 2

Make the cheesecake batter. Beat cream cheese in a medium bowl with an electric hand mixer or spatula until smooth. Add sugar and vanilla and beat until very smooth glossy. Beat in egg until well incorporated and set aside.

Step 3

Make the brownie batter. Combine chocolate and butter in a saucepan over very low heat and stir constantly until melted and smooth, or melt in the microwave at 50% power in short bursts with frequent stirring.

Step 4

Combine eggs, sugar and salt in a large bowl and whisk or beat with an electric hand mixer until pale and thick. Beat in warm melted chocolate mixture. Whisk together flour and cocoa powder and sprinkle it over the surface and fold it in until evenly combined. Reserve about 1/3 cup (80ml) of brownie batter and then spread the rest evenly into prepared pan.

Step 5

Spread the cheesecake batter evenly over the brownie batter in the pan, then dollop teaspoons of reserved brownie batter randomly over top. Swirl it in with a knife to create a marbled effect.

Step 6

Bake for 10 minutes. Reduce oven to 325°F and bake for another 15-20 minutes for a 9-inch pan until puffed and the cheesecake is set in the middle with lightly golden edges. If you use an 8x8 inch pan, then add another 3-5 minutes to the baking time. Transfer pan to a wire rack and let cool completely in the pan. Refrigerate for at least 1 hour before slicing with a hot dry knife.