Preheat your oven to 325°F. Line an 8x8-inch metal baking pan with parchment paper, leaving a 2-inch overhang on each side.

To make the brownie batter, gently melt chopped dark chocolate with butter in a heatproof bowl in the microwave or in a saucepan over the stove until completely melted and smooth. In a separate bowl, whisk together egg, egg white, sugar and vanilla until thickened and pale in colour. Add the warm chocolate mixture and whisk until well incorporated and batter is smooth and glossy. Mix in salt and flour until evenly blended. Reserve about ¼ cup of batter and spread the rest evenly into your prepared pan.

To make the cheesecake mixture, beat cream cheese with brown sugar in a medium bowl until smooth and glossy. Mix in egg yolk, sour cream, molasses and spices until creamy.

Spread the cheesecake mixture evenly over the brownie batter in the pan. Dollop small spoonfuls of reserved brownie batter randomly over the surface and use a wooden skewer to swirl it in. Sprinkle chopped chocolate over top.

Bake for 30-35 minutes until slightly puffed and a toothpick inserted into the center comes out with a few moist crumbs. Let brownies cool completely in the pan before slicing with a hot dry knife.