Grease and line a 30x20 cm tray with baking parchment
Add chocolate and butter to a heatproof bowl and put in the oven as it heats up, stirring occasionally until melted
Add sugar, beetroot, eggs, cocoa powder, salt, flour and nuts to a bowl. Use a blender or food processor to blitz until combined. Alternatively, stir ingredients for chunky beetroot pieces
Spoon mixture into lined baking tray and spread evenly
Bake for 30-45 minutes until the top is firm to the touch