1 medium onion, finely sliced
600g waxy potatoes such as Jersey Royals or Charlottes, peeled, halved and cut into thin slices (like thick crisps)
6 medium eggs, beaten
Salt and pepper
2 tbsp extra virgin olive oil
1. Heat the olive oil in a large frying pan over a medium flame, add the onion and cook gently for 20 minutes until soft and brown. Rinse the potato slices under cold water and pat dry. Add the potato to the pan – if it seems overcrowded, you can cook them in a couple of batches. Cook until the vegetables are tender and on the point of falling apart, then drain well, keeping the oil for your next omelette.
2. Add the potato and onion to the beaten eggs, season well, and leave to stand for 10 minutes, or longer if you prefer a stronger onion flavour.
3. Put a smaller pan (about 22cm) over a medium heat and add the extra virgin olive oil. Turn to coat, and then, when hot, add the mixture – it should almost fill the pan. Cook until it comes away from the edge of the pan, and looks about two thirds set.
4. Place a plate, or a saucepan lid, over the pan, and invert it so the tortilla flips on to the plate. Slide it back in, tipping any liquid egg in with it. Cook until it is springy to the touch: be careful not to overcook it: it should still be moist in the middle, even if you prefer it cooked right through.
