Preheat your 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 bowl and leave to cool
Whisk together the eggs and sugar for a few minutes until the colour has turned pale, is very mousse like, and is double the original volume of the amount
Pour in the cooled dark chocolate and unsalted butter mix over eggs and fold together carefully
Add the flour, cocoa powder and mint extract and fold in again
Once combined well, fold through the milk chocolate chips and oreos
Pour evenly into the prepared tin and bake in the oven for 25-30 minutes
Once baked, leave to cool in the tin completely for at least 2 hours, or overnight in the fridge. Enjoy!
Notes
These will last for 3-4+ days in the fridge or at room temperature