First quarter the peeled potatoes, then cut into slices that are not too thin. Halve the onions and cut into large pieces. Heat 2 tablespoons of oil in a pan and fry the potatoes and onions (seasoned with pepper and salt) for 15 minutes.

Put the eggs in a sufficiently large bowl and stick them together thoroughly with the mineral water, pepper and salt. Fold in the potato and onion mixture.

Heat the olive oil in the pan again, add the egg mixture, put a lid on the pan and cook the tortilla over a mild heat for about 8 minutes. Turn it over and let it brown appetizingly on the top as well.

I served my tortilla today with onion slices and tart olives garnished with leaf spinach ... really Spanish !!.