Preheat oven to 370℉/180℃. Line either a brownie pan (as seen in my photos) or a regular 8x8" baking pan using baking paper/spraying with oil.
Melt the dark chocolate by breaking up into small pieces in a bowl and heating for 30 second intervals in a microwave, stirring in between. Alternatively, set up a double boiler. Do this by placing a heatproof bowl over a small pot of simmering water. Add the chocolate to the heatproof bowl and stir until melted. Set aside to cool whilst making the brownies.
In a large bowl or the bowl of a stand mixer combine the melted butter, and both sugars until totally combined.
Add the eggs and mix again. Then check that the dark chocolate has cooled a little before adding in and combining. Add in the flour, cocoa powder and fold together. Pour into the prepared pan.
Make the cheesecake layer: combine all ingredients in a small bowl. Pour this over the brownies. Swirl using a knife or chopstick. Bake:Bake time - Regular 8" square Pan: 27-30 minutesIndividual Brownie Pan: 20 minutes Remove and let cool before serving! If using an 8" baking pan, wait until cool before slicing!