Pre-heat your oven to 160C Fan/350F/Gas Mark 4 and grease and line a 12" x 9" traybake tin
To make the cheesecake swirl, mix together the full fat cream cheese, caster sugar, egg and vanilla extract with a hand whisk or electric hand whisk until smooth. Add enough orange food colouring to get a bright shade. Set aside
For the brownie mix start by melting the dark chocolate and butter in a pan on a low heat, once melted stir together then set aside to cool for 5-10 minutes
In a large mixing bowl, use an electric mixer to mix together the dark brown sugar and the eggs until frothy - this takes about 5 minutes
Slowly pour the melted chocolate and butter into the egg mixture, whilst constantly whisking - either with a hand or electric mixer
Add the plain flour and gently whisk in
Add enough black food colouring to get a dark shade, gently stir it in
Pour about two third of the brownie mixture into the traybake tin, then add the cheesecake mixture on top, then spoon the rest of the brownie mix on top in blobs
Using a butter knife, swirl the mixture around to create a swirl pattern, then bake it for 30-35 minutes
Leave it to cool completely then refridgerate before removing from the tin and cutting into squares
Store in the fridge and eat them within 3 days