1) Sauté the onion and bacon in the oil in a large frying pan for a few minutes.
2) Add the potatoes, courgettes and mushrooms. Cook for 2 -3 minutes.
3) Add the tomatoes and cook for a further 2 minutes.
4) Season the beaten egg, mix with the milk and pour over.
5) Make sure the ingredients are evenly spread out and cook over a gentle heat until set.