Spanish Potato Omelette

Peel the potatoes, slice them into rounds that do not need to be very thin, and leave them soaking in water.

Slice the onion.

Set out two pans: a medium one for the onion and a large one for the potatoes. Add a little oil, the onion, and salt to the medium pan. Cover and cook gently over medium heat. In the large pan, heat enough oil to cover the potatoes, add the potatoes, and cover. Leave both pans cooking over medium heat for about 40 minutes without stirring. The potatoes should break apart at the lightest touch.

While they cook, crack the eggs into a large bowl, the bowl that will later hold the whole mixture. Beat them gently without incorporating air for a creamier tortilla.

Uncover the onion, raise the heat to evaporate its water, and let it caramelize a little, but not too much. Remove it and drain away its oil and moisture in a colander.

Drain the oil from the potatoes, reserving it to filter and reuse if you like. Leave a little oil in the pan, raise the heat, and season with salt. Constantly move and break up the potatoes until they form a fairly even mixture, toast just a little, and become very hot. That heat will cook the egg later.

Immediately add the very hot potatoes to the bowl of eggs and mix well. Add the onion too, then let the mixture rest for 5 minutes. The egg cooks here, rather than later while the tortilla sets.

Lightly oil the onion pan, or another medium pan, coating it well so the tortilla releases easily. Heat over medium heat, add the mixture, and cook for 3-4 minutes until a thin layer has set. Turn it out onto a plate, optionally rubbed with a little oil so it slides back easily, then return it to the pan and cook the other side in the same way.