Preheat your oven to 180 degrees Celsius and then place the butter, chocolate and beetroot into a food processor and blitz until combined.

Place the caster sugar, vanilla sugar and eggs into a large bowl and whisk until frothy and pale.

Mix together gently with the beetroot, chocolate, and butter and then add in the flour and cocoa powder and fold in until well combined.

Grease and line a large, square baking tray with greaseproof paper, and then pour in the batter.

Place into the oven and bake for about 25 minutes. Remove and allow to cool completely in the tin before cutting into squares and enjoying.