There are dishes born of necessity that stuck around because they are delicious. Marmitako is exactly that - a Basque fisherman's stew that came to be on the boats, when fishermen from the Bay of Biscay needed something simple, hearty and warm for the long days at sea. The name comes from "marmita", the Basque word for a pot. In it, tuna, potato and vegetables come together as one - seemingly plain, but actually precise.

For four servings you need about 400 grams of tuna without skin and bones, extra virgin olive oil, one red and two green peppers diced, an onion, three cloves of garlic, five larger potatoes, a spoon of dried pepper pulp (choricero), a cup of homemade sauce, a piece of bread, a little hot pepper, a teaspoon of smoked paprika, a splash of white wine, a litre of fish stock and parsley.

The secret is not in the ingredients, but in a single move. The potatoes are not cut - they are broken with a knife, so they release more starch which later thickens the stew naturally, without additives. First the garlic, onion and peppers are sauteed for about ten minutes, the broken potatoes go in for another four or five, then the tomato, the peppers, the bread and the hot pepper. The wine is poured in to evaporate the alcohol, then the stock, and it all simmers for about 30 minutes until the potato softens.

The tuna goes in last, and there lies the second key. It is cut into cubes of about 4 centimetres, briefly seared separately so it catches colour on the outside while staying almost raw inside, and added to the pot only three to four minutes before the end. If you cook it long, it will dry out - the tuna in marmitako melts in your mouth only if you respect it. A simple dish that asks for a little patience and one technique - exactly as a good stew should.