Procedure:
Wash the potatoes, peel and cut into slices. In a bowl beat the eggs with the grated Parmesan cheese and a pinch of salt and black pepper. In a non-stick pan let simmer for a few minutes finely chopped onion with oil and a little water. Add potatoes and sauté a few minutes to season them.
Add about 50 ml of water, a pinch of salt and the rosemary. Cook (the first few minutes with the lid on) until the liquid is almost completely absorbed and will be potatoes are cooked through but still very firm. Place the potatoes with the remaining liquid into the bowl with the eggs and stir everything gently.
Pour the extra virgin olive oil in a pan and when hot , pour the mixture.
Cook over low heat with the lid on for about 10 minutes, turn the omelet with the aid of the lid, and cook the other side. Cook a few minutes also this other side.
The potato omelette is ready!