Lay your grated beetroot, carrot and cannellini beans on an oven tray. Spray with olive oil and sprinkle with a pinch of salt, then pop in the oven at 200c/392f until wrinkled and slightly charred. (approx 15mins)
Once cooled, add your beans, egg and lemon juice in a food processor and blend to a paste.
Combine in a bowl with your carrot, beetroot, green onion, mint, cashews, feta, half of your breadcrumbs and generous amounts of salt and pepper.
Take a small pinch of your mixture and mould a tiny burger shape (use gloves if desired). Fry until golden then test for seasoning/texture. For a more moist burger add more lemon juice, to dry out the burgers add more breadcrumbs.
When happy, mould 4 burger shapes and shallow fry in a good glug of oil over medium heat until dark golden colour, flipping once.
Stack with your desired toppings and enjoy!