Heat olive oil in a skillet over medium heat. Slice the onion thinly, add it to the skillet once the oil is hot, cover, and cook until softened. You can add more onion if you like.

Meanwhile, peel the potatoes and cut them into thick slices. When the onion is soft, add the potatoes and salt, stir a couple of times, cover, and cook over low heat until the potatoes are tender.

In a bowl, beat the eggs and add a splash of milk. Mix well.

When the potatoes are very soft and break apart easily, drain them well to remove excess oil and add them to the eggs. Mix well and let sit for about five minutes.

Meanwhile, pour the drained oil back into the skillet. When hot, add the potato and egg mixture. Cook over low heat until set on one side, then flip and cook until both sides are golden and the omelette is cooked through.