Spanish potato omelette (Tortilla española)

1. Peel the potatoes, quarter them and slice thinly (2-3 mm); slice the onion into thin half-moons.

2. Heat the olive oil in a 24 cm frying pan until medium-hot, add the potatoes and onion, season and confit over medium-low heat for 20-25 minutes, turning occasionally – the potatoes should be soft but not browned.

3. Tip into a sieve to drain the oil (keep it), beat the eggs with salt in a large bowl, stir in the still-warm potatoes and leave for 10 minutes so the egg soaks in.

4. Heat 2 tablespoons of oil in the pan, pour in the mixture and cook over medium heat for 4-5 minutes, tucking the edges in with a spatula.

5. Put a large plate over the pan, flip it over in one confident movement and slide the tortilla back in to cook the other side for 2-3 minutes.

6. Serve warm, cut into wedges – the real thing is slightly creamy ("jugosa") inside.

Tip: Keep the drained potato oil: it's great for frying or roast potatoes next time.