Ingredients:

800 g/1-3/4 lb potatoes
5 tablespoons olive oil
2 large onions, sliced
salt
6 eggs
freshly ground black pepper

Methods:

Peel and cut the potatoes into 5 mm/1/4 inch thick slices. Reserve about 1 tablespoon oil and heat the remainder in a large frying pan with sloping sides, preferably nonstick. Add the potatoes and onions, season lightly with salt, cover and cook over a medium-low heat for about 15 minutes, until the vegetables are tender-toss occasionally during cooking with a spatula. Let cool for 10 minutes.

Beat the eggs with 1/2 teaspoon of sat and pepper to taste in a large bowl. Fold in the potato and onion mixture. Wipe the frying pan with kitchen paper and add most of the reserved oil. Heat well and pour in the egg mixture. Flatten the top with a spatula and cook over a medium-low heat for about 5 to 8 minutes, until the omelet is browned underneath and the top is set around the edges. Loosen the edge of the omelet with a spatula and shake the pan to check that it has not stuck. Slide it out onto a plate. Brush the pan with the remaining oil, about 1 teaspoon. Place the pan over the top of the plate and invert the omelet back into the pan. Return to the heat and cook for 3-4 minutes, until the base is lightly browned.

Alternatively, leave the partly cooked omelet in a frying pan and place under a heated grill-protect the handle with foil. Grill until lightly browned and then slide the omelet onto a serving plate. Serve hot, cut in wedges.Alternatively, leave to cool and cut into 2.5 cm/1 inch cubes and serve as a tapa dish.