Spanish Omelette (Tortilla Española)

Method

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1. 1Halve the potatoes and slice them 3–4 mm thick, thinly slice the onion, and toss both with 1/2 tsp salt.
2. 2Heat the olive oil in a 22–24 cm non-stick pan over medium-low heat; a slice of potato dropped in should bubble gently, not sizzle hard.
3. 3Add the potatoes and onion and cook for 20–25 minutes, stirring now and then, until the potatoes are tender enough to crush with a fork but not browned.
4. 4Drain the potatoes in a sieve set over a bowl and let them cool for 1–2 minutes; keep the oil.
5. 5Beat the eggs with the remaining salt in a large bowl, stir in the potatoes and leave for 10 minutes so they soak up the egg.
6. 6Heat 1 tbsp of the reserved oil in the same pan over medium heat, pour in the mixture and cook for 4–5 minutes, tucking in the edges with a spatula, until the base is golden and the top still runny.
7. 7Cover the pan with a flat plate larger than the pan, flip it over in one confident motion, then slide the tortilla back in, uncooked side down.
8. 8Cook the second side for 2–4 minutes: shorter for a soft, juicy centre, longer for a fully set one.
9. 9Slide onto a plate and rest for at least 5 minutes; serve warm or at room temperature, cut into wedges.