Preheat the oven to 180ºC/160ºC fan and line a 9″ square baking tray with parchment paper.
Melt together the unsalted butter and dark chocolate in a heatproof bowl over a pan of boiling water, or in the microwave in short bursts until melted.
Leave to the side to cool to room temperature.
In a new bowl, whisk together the eggs and caster sugar for a few minutes until the colour has turned pale, is very mousse like, and is double the original volume of the amount of eggs + sugar! You will know its done because when you lift the whisk up out of the mix it should leave a trail for a couple of seconds!
When whisked, pour the cooled dark chocolate/unsalted butter mix over your egg and sugar mix and fold together carefully. It might take some time, but be patient – you don’t want to knock out the air you made up on the previous step
Once completely combined, add the cocoa powder and plain flour on top of the chocolate mix and then fold together again – still being careful to not knock out the air!
Once combined well, fold through the milk chocolate chips evenly and pour 90% of the mixture into the prepared tin.
In a bowl, beat the cream cheese until loose, and add the caster sugar and beat again until combined.
Gradually beat in the egg until combined along with the vanilla extract.
Pour the cheesecake mixture on top of the brownie mixture, add the last bit of brownie mixture in dollops and swirl slightly.
Bake in the oven for 25-30+ minutes, until there is a slight wobble in the middle! Once baked, leave to cool in the tin completely.
Notes
This recipe will last covered in the fridge for 4-5 days, or you can freeze them for up to 3 months!.
I used milk chocolate chips in my brownies to give it a bit of an extra hit, but this is optional!
I used Philadelphia full fat cream cheese, but any brand is fine providing it is full fat!
Any dark chocolate is fine to use in the brownie mixture, providing it is at least 70% cocoa.