Preheat the oven to 180ºC/160ºC fan and line a 9″ square baking tray with parchment paper.
Mix the finely crushed oreos with melted butter and press into the base of the lined tin.
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 and sugar
When whisked, pour the cooled chocolate mix over your egg and sugar mix and fold together carefully
Add the cocoa powder and plain flour on top of the chocolate mix and then fold together again
Pour the brownie mixture over the oreo base
In a new bowl, beat the cream cheese until loose, and add the caster sugar and vanilla and beat again until combined.
Gradually beat in the egg until combined. Then stir through the oreos
Pour the cheesecake mixture on top of the brownie mixture, and swirl slightly. Sprinkle over some extra oreos if you fancy.
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, and then in the fridge for 4-5+ hours, but preferably overnight.
Notes
This recipe will last covered in the fridge for 4-5 days, or you can freeze them for up to 3 months!
Any dark chocolate is fine to use in the brownie mixture, providing it is at least 70% cocoa.