Separate the eggs and stick the yolks with salt and a little freshly grated nutmeg. Beat the egg whites until stiff. Clean the mushrooms and cut into fine slices, dice the onion and chop the parsley.

Mix half of the parsley into the egg yolk. Heat the butter in a pan, fry the onions until translucent, then add the mushroom slices and fry briefly. Season with pepper and salt and place half of the onion mushrooms on a plate and cover.

Spread the rest of the mixture in the pan, mix the egg yolk mixture with the egg whites and pour over the mushrooms. Put a lid on the pan and let the omelette set over a mild heat (it should still be a little juicy on the top).

Place the reserved mushrooms on one half of the omelette, fold over the other side, slide the omelette onto a warmed plate and serve sprinkled with the rest of the parsley.

A mushroom omelette is an extremely quick meal and Grandma also liked it when someone was sick - as a particularly light meal, but also invigorating and healthy!