Ask most Spaniards what a romescu is and they will almost certainly say one of Spain’s most famous sauces, used mainly for fish although it also pairs nicely with some meats, especially rabbit. But that is less than half of the story because it leaves out the important origins of the word romescu.

Romescu is, first and foremost, a Catalán dish in which a variety of fish is cooked and it gets its special taste from a picada which contains a dried red pepper. But not any old red pepper. This one is known as pebrot de romescu and it is grown only in the Tarragona area.

It’s a smallish livid red pepper that tapers off to a flattish point. Despite its size, it is fleshy and it’s this pulp that helps to give the dish its characteristic taste.

This fish dish, which is known in Tarragona as romescu de peix, is a speciality in a limited area along the coast from Torredembarra to Cambrils.

In the opinion of the experts, the best place to eat this fish stew is in the old fishermen’s quarter of the city of Tarragona known as Els Serralls. It’s there every year that they hold a contest to find the mestre romuscaire, the master romescu maker.

The winner is usually a man from a fishing family, getting on in years, and with decades of experience in making a romescu de peix. This experience is important because the best romescus are made with a picada that is passed on from father to son and never revealed to anyone outside of the family.

It’s this secret formula that determines the fish stew’s final taste and character. As with most other secrets of this kind, it’s a combination of known ingredients rather than any one special herb or spice.

As the picada contains roasted nuts and herbs such as thyme, fennel and oregano, the amounts of each ingredient can completely change the final taste. I have written about picadas on many occasions and I always say they are usually added to a dish when it is ready, in order to give a final explosion of concentrated flavour.

The romescu de peix is one of the exceptions — the picada is added with the stock at the beginning and the fish is cooked in it.

The fish used in a romescu de peix are mainly the firm white ones such as monkfish (rape), sea bass (lubina), turbot (rodaballo) and conger eel (congrio). What they all have in common is that they don’t fall apart when cooked. Some cooks also include tuna (atún) and skate (raya).

The making of this picada is like the others in that the ingredients are pounded in a mortar until they form a smooth paste. It is then added to a saucepan or a greixonera and is cooked for 10 minutes in a little stock.

More stock is added and sometimes a small amount of chopped hot chilis, plus a glass of red wine and one of brandy. The mixture is simmered for another 15 minutes and the pieces of fish are carefully placed in the saucepan. From this point on the fish will not be stirred or moved in any way.

Any final seasoning is added, the stock is brought to the boil, the saucepan is covered, and simmered for only 10 minutes. It is then taken off the heat and left for two hours. It is gently reheated just before serving.

Unlike many of the dishes I write about, the origins of romescu de peix are not lost in remote times. One writer had it that King Jaime I ate a romescu de peix before setting sail for Majorca in 1229 to recapture the island from the Moors.

We know this is not true as peppers did not exist in Europe until Columbus brought them back from his second visit to the New World. The dish is first recorded in a cookbook called El Cronicón published in 1884, although the romescu de peix obviously existed long before that.

There are amateur cooks who always want to ‘improve’ a dish with what they consider to be inspired changes, either in the ingredients or the cooking method. Many professional cooks are always on the lookout for ways of making life easier for themselves — by taking short cuts and changing the essential character of a dish.

At some time or other a restaurant cook had the idea of using the romescu picada as a sauce to serve with fish. The idea caught on and in restaurants outside of Tarragona a romescu became a sauce served with grilled fish, often lobster. This romescu was a long way from the original fisherman’s fish stew. However, the sauce does exist, it does pair nicely with fish and there’s no reason why we shouldn’t make the most of it.

As the dried peppers used for this dish are difficult to find outside of Tarragona, we could use the dried peppers called ñoras. But most cooks nowadays would use ñora paste sold in small jars at El Corte Inglés and some other supermarkets. So that’s what I’ll give in the following recipe.

You will need: 250mls virgen extra olive oil, ñora paste, 1 slice of crustless Majorcan pan moreno, 2 or 3 garlic cloves simmered in a small amount of water for five minutes, about 20 roasted almonds or hazelnuts.

Fry the bread on both sides until crisp and golden. Put the bread, garlic cloves and ñora paste into a mortar and pound until smooth. Add the nuts and continue to pound until the bread and garlic are well crushed.

Add some virgen extra olive oil, a spoonful at a time, and mix it well into the other ingredients. Keep adding the oil until you have a thick smooth sauce. Stir in salt to taste.

If you want the picada for doing a fish stew, do not use the olive oil. Instead, stir in a little stock to give a smooth picada and then add it to the stock in which the fish will be cooked.

This is a basic picada and most cooks include parsley or other herbs of their choice, paprika (pimentón dulce), black pepper, red wine or even a touch of vinegar. Some cooks like to include a biggish roasted tomato, skin and seeds removed. Add it at the beginning and pound it with the bread and the garlic.

The sauce is sometimes heavily flavoured with raw garlic and some cooks make it very piquant by using a larger quantity of hot chilis. But this sauce is meant to enhance fish, not overwhelm it. It should be a delicate well balanced sauce.

Most housewives nowadays dispense with the mortar and pestle and blitz the ingredients in a blender. It’s quicker that way but the sauce doesn’t have the same deliciously gritty texture.

You should remember the quantities you use of every ingredient so you can vary them and give the sauce your own special flavour.