The famous chef Juan Mari Arzak once declared that for him Spanish cuisine was the best in the world, that Basque cuisine (including Navarra) was the best in Spain and that the best food in the Basque Country could be found in San Sebastián. And what could be more representative of the city’s culinary heritage than salsa verde?

This quintessential sauce has been present at some of the city’s most important turning points. For example, when its residents reclaimed Mount Urgull, a promontory in the heart of the city, with the River Urumea to the right and La Concha beach to the left.

No longer suitable for military use, when the mount was returned to the city in August 1921, a famous banquet was served for the authorities, presided over by the president of the government, Sánchez Guerra. According to Sandalia González Palacios’ account in A Brief history of food and cuisine (Breve historia de los alimentos y la cocina), one of the main courses at the meal was kokotxas (a cut of hake from the throat or the chin) served with salsa verde.

In culinary theory, it’s commonplace to seek out the basic sauces of a country’s repertoire. Marie-Antoine Carême did this for France in the 19th century, somewhat paradoxically including espagnole and allemande alongside béchamel and velouté.

Basque cuisine also has its own quartet of fundamental sauces: salsa verde (green sauce) is one, alongside blanca (white, or pil-pil), roja (red, or Basque-style, made with choricero peppers) and negra (black, made using squid ink). Salsa verde, however, is special, in that it has its own unique origins. Legend has it that the recipe was first written down in 1723 by Plácida de Larrea, who lived in Biscay, in a letter to Plácida Larrinaga, her namesake in the valley of Baztán. The recipe describes hake in a green sauce, with an abundance of parsley, asparagus, baby clams and crabs.

Perhaps it was the former’s origins in the region of Biscay that led Emilia Pardo Bazánin, author of the classic recipe book Ancient and modern Spanish cooking (La cocina española antigua y moderna), to coin the term “Biscay style” to describe what is in fact “San Sebastián style”, or, in other words, hake served with salsa verde.

Regardless, the recipe has enjoyed great success and remains a stalwart of menu’s in San Sebastián to this day, even though its humble origins as hake with a sauce made with of oil, garlic, flower and parsley have given rise to more sophisticated developments such as koskera hake, which is served with asparagus, peas and boiled egg, or, nowadays, more commonly with kokotxas.