I have been making this tortilla for years, it is a real store cupboard recipe. Waxy potatoes are a must, floury ones like King Edwards will fall apart and leave you with just oniony mashed potatoes. Older new potatoes are ideal, as they are waxy, but less work than new potatoes because they are bigger. Slice them lengthways as thinly as you can, or use a mandoline.
Serve with salad and a mild cheese like Ossau Irraty or Manchego and membrillo.
500g onion, thinly sliced
750g waxy potatoes, scrubbed (not peeled) and sliced thinly, 3mm thickness
3 eggs, beaten
Salt and pepper
2 tbs fresh oregano, chopped
Boil the potatoes for seven minutes in salted water. They should be just cooked, but not falling apart. While they are cooking, gently fry the onions in oil and a pinch of salt until they are soft, sweet and browning.
Drain the potatoes and put them back into the dry pan over a low heat for a couple of minutes. This is so they dry out as wet potatoes will cause you trouble. Don’t take your eyes off of them or they will burn. Mix in the cooked onions and stir in the beaten eggs and pepper, do this gently so you don’t break up the potatoes.
Heat the oil in a decent non-stick frying pan. Once the oil is hot, add the potato, onion and egg mixture, squashing it down into the pan a little. Turn the heat to medium and wait for the eggs to cook. Use a spatula or fish slice to look under the tortilla.
Once it is browning, you are ready to turn it over. Loosen the tortilla all the way round with a blunt knife. Turn the heat off, place a large plate over the pan and a rolled up tea-towel over that. Turn the pan upside down, the tortilla should come out cleanly. Wipe the pan down with kitchen towel and heat another tablespoon of oil. Once hot, slide in the tortilla to cook the other side. Once both sides are cooked, serve onto a plate, season with salt and oregano. Wait for it to cool. You can serve it at room temperature or cold.
Add 1/2 red pepper, thinly sliced and cooked with the onions.
Add a clove of garlic to cook with the onions.
Add a couple of slices of Serrano ham, shredded.
Add chives or parsley instead of oregano