Heat oven to 190C/170C fan/gas 5. Tip the butter beans into a bowl and mash with a fork to form a rough puree. Set aside. Heat 1 tbsp of oil in a small frying pan and add the onion and garlic. Cook over a gentle heat for 3-4 mins, until softened.
Stir the onion mixture into the butter beans, along with the cheese, then season. Shape the mixture into 4 patties, cover and chill for 10 mins.
Put the cherry tomatoes in a small roasting tin and season with salt and pepper. Roast for 10-15 mins, until tender.
Tip the flour, egg and breadcrumbs onto three separate plates. Roll each patty in the flour, dusting off any excess, carefully roll in the egg, then finally coat in the breadcrumbs.
Heat remaining oil in a non-stick frying pan and add burgers. Cook for 8-10 mins, turning occasionally until golden. Drain on kitchen paper and serve with the roasted tomatoes and rocket.