Peel the potatoes and grate on a coarse grater (in the original Italian recipe cut potatoes very thin with a special tool)

In a frying pan (preferably Teflon coated) heat the olive oil and lay the potatoes neatly. Fry until almost Golden brown (in the original Italian recipe, the potatoes are roasted), reduce the heat to low. Add the diced onion and dried rosemary. Fry until soft onions, stirring constantly.

In a separate bowl beat the eggs with salt and ground pepper, add the Parmesan cheese, mix well and put in a lot of potatoes. Mix well and spread in a round baking dish. Put in a pre-heated oven for 10 minutes at 200°C.

After 10 minutes, remove the omelet from the oven, sprinkle with grated cheese (cheese can take on Your taste, you can also make a mix of several varieties). Put back in the oven for 7-10 minutes (until Golden cheese crust).