Tortilla Española (Spanish Potato Omelette)

Cut the potatoes750 g into thin slices, about 3 mm, and pat them dry with a tea towel. Halve the onions2 and slice them thinly.

Heat the olive oil500 ml in a deep frying pan about 24 cm across. Add the potatoes and onions, turn the heat down and cook gently for about 20 minutes, turning now and then, until the potatoes are soft but not browned.

Meanwhile, crack the eggs8 into a large bowl, add the salt1 tsp and pepper¼ tsp and whisk.

Drain the potatoes and onions in a sieve set over a bowl to collect the oil, then stir them into the beaten eggs.

Wipe out the pan and heat 2 tbsp of the collected oil. Pour in the egg and potato mixture, turn the heat down and cook for about 4 minutes, until the bottom has set and the top wobbles but is no longer runny.

Cover the pan with a large plate, turn it over in one quick move, then slide the tortilla back into the pan, uncooked side down.

Cook for about 4 minutes more, until just set in the middle.

Slide onto a plate and leave to rest for 15 minutes before cutting into wedges.