Peel the potatoes and slice thinly. Cut the onion in very small pieces and add to the potatoes. Fry potatoes and onions in a generous amount of oil over a low heat, removing them with a palette knife when cooked and drain well. In a separate bowl, beat the eggs and mix with the potatoes. Leave for a few minutes so that the eggs fully absorb the potatoes.
Heat a pan with a Tbsp. of oil and then pour the mixture into the pan, over a low heat and let it thicken
Use a big flat dish or a lid to turn the mixture over and allow to cook on the other side.