Tortilla Espanola

Steps

1. 1
   Slice the potatoes into thin, uneven rounds — a mandoline is too regular and gives a dense tortilla.
2. 2
   Heat the olive oil in a 24 cm pan to a bare shimmer, around 130°C. This is poaching, not frying: the potatoes should never colour.
3. 3
   Add the potatoes and onion and cook gently 20-25 minutes, turning occasionally, until completely tender and breaking at the edges.
4. 4
   Drain them in a colander, reserving the oil, and season generously.
5. 5
   Beat the eggs in a large bowl, tip in the hot potatoes and let them sit for 10 minutes so the egg starts to thicken around them.
6. 6
   Return 2 tbsp of oil to the pan over medium heat, pour in the mixture and cook 4 minutes, drawing the edges in.
7. 7
   Slide onto a plate, invert the pan over it and flip the tortilla back in. Cook another 3-4 minutes.
8. 8
   Rest at least 15 minutes. The centre should stay slightly loose — a dry tortilla is an overcooked one.