Preheat the oven to180ºC. I’ve used a rectangle baking tin to make these, but you can also use an 8x8 inch tin (however you will need to bake it for a few minutes longer). Line the tin with baking paper generously so it over laps on the side
In a food processor add the chocolate biscuits and blend until fine. Transfer to a mixing bowl, add the melted butter and stir to combine, the mixture should resemble wet sand. Dump into the baking tin and flatten the mixture evenly using your hands or the back of a spoon. Ensure it covers the tin in one single layer.
Melt the butter or brown the butter, add the chocolate and stir until combined. Allow to cool a little.
In a large mixing bowl, beat the eggs with sugars until pale, creamy and fluffy. Add the vanilla, oil and whisk again. Add the cooled chocolate butter mixture and whisk until combined.
Add the flour, cocoa powder, salt, baking soda, vinegar and stir until combined and no dry ingredients are visible. Pour 3/4 of the batter into the baking tin and set aside.
In another mixing bowl add all the ingredients for the cheesecake and beat until combined, do not over mix. Dollop the batter into the baking tin and top with the remaining red velvet batter.
Using a knife, tooth pick or spatula make swirls in the brownie and don’t over do it at this stage. Place into the oven and bake for 28-30 mins until the sides are set and the center is dry on the top but still has a giggle.
Let it cool in the pan before cutting into squares and serving.