Place the drained cannellini and kidney beans in a large bowl and mash together. Heat 1 tablespoon of the oil in a frying pan. Add the spring onions and fry for 2 minutes. Add the mushrooms and cook for a further 4 minutes Tip into the bowl of beans; mix well.
Place the broad beans in a pan of boiling water and cook for 2 minutes. Drain, then add to the bean mixture along with the oats, Worcestershire sauce and tomato purée. Season with ground black pepper and mix together. Divide the mixture into 8 and shape into patties. Freeze 4 for another time (see tip).
Heat the remaining oil in the frying pan and cook the bean burgers for 10 minutes, turning once, until golden and warmed through. Serve in the rolls with the lettuce, tomatoes and mayonnaise, with the coleslaw on the side.
Cook’s tip: to freeze the extra patties, simply put on a tray, cover, and place in the freezer. Once frozen, put in a freezer bag. Keep for up to 3 months. Defrost and cook as in step 3.