Boil the potatoes for 6 mins or until just cooked, then drain and set aside. Heat the oil in a large, deep, ovenproof frying pan and fry the courgettes for 4-5 mins until golden. Tip in the potatoes and fry for 1 min with the courgettes.
In a bowl, beat together the eggs and mint, then season. Pour into the frying pan and stir briefly. Cook for 5 mins over low heat. Crumble over the cheese and finish under a hot grill for 5 mins, until the eggs are just set and the cheese is browned. Cut into wedges and serve.