For the stew, heat two tablespoons of the oil in a casserole pan and fry the onions, courgettes, celeriac and garlic for 4-5 minutes.
Add the tomato purée and smoked paprika and cook for a further 4-5 minutes. Add the chopped tomatoes and stock, bring to boil, then reduce to a simmer for 20-25 minutes.
Stir in the butter beans, basil and lemon zest and cook for a further 10 minutes, then stir in the broad beans. Finish the stew with a good glug of extra-virgin olive oil.
Meanwhile, for the griddled potato cakes, mix the ingredients together in a bowl until well combined, then shape the potato mixture into six patties.
Heat the oil in a frying pan and fry the patties for 3-4 minutes on each side, or until crisp and golden-brown on both sides.
To serve, ladle the stew into serving bowl and serve the potato cakes alongside.