For the egg dish, whisk the eggs with a dash of mineral water, pepper and salt very little. Dice the feta cheese and mix it in. Peel, wash and finely chop the onion.
Heat the butter in a frying pan and lightly fry the onion cubes in it. Add the egg and feta cheese mixture, stir gently and cook over medium heat for about 5 minutes.
Divide among warmed plates, sprinkle with parsley and serve with wholemeal bread or fresh pastries.