1) Heat half the oil in a large frying pan over a medium heat. Add the aubergine slices and cook until browned on both sides. Transfer to a plate and cut into 1 inch pieces.
2) Heat the remaining oil in a large saucepan over a medium heat. Add the onion and peppers. Cook, stirring frequently, until the onion has softened. Add the garlic and cook for a further 2-3 minutes.
3) Add the tomatoes, cumin, oregano and chilli powder. Bring to the boil and then reduce the heat, cover and simmer gently for 15 minutes.
4) Add the courgettes, aubergines, beans, water and tomato puree to the pan and return to the boil. Reduce the heat, cover and simmer for a further 45 minutes.
5) Serve topped with the spring onions and cheese. Serves 4.