But almost always, it seems, traditions are maintained, even as they are subverted. Victor Arguinzoniz, the chef at his restaurant, Asador Etxebarri, excels at grilling over flame — and has designed his own equipment to do so. He may use a dusting of ash to enhance even the butter on the table.

“The Basque language changes every 10 kilometers, and I think the same happens with our food,” Mr. Atxa said. “What we probably all have in common, however, is growing up in Basque homes in which life has revolved around the kitchen rather than the living room.”

Certainly, the area offers enough to choose from. Elena Arzak, Mr. Arzak’s daughter and partner, has been visiting San Sebastián’s main food market since her early childhood. But however often she goes, Ms. Arzak explained, there is always something to be recalled or learned anew.

Depending on the season, she may find all kinds of regional specialties, like hake kokotxa, the fleshy underpart of the fish’s jaw, or live baby eels — not for the squeamish.

“So much is available here that I often forget exactly what is best during what season,” she said as she checked the ripeness of a green Errezil apple, a local variety.

In fact, every aspect of life in San Sebastián seems to revolve around food, from the gastronomic societies that are a less formal equivalent to British gentlemen’s clubs — and where members do their own cooking — to the small bars that serve pintxos, the Basque version of tapas, in the city’s historic center.

“It’s extremely rare to have a place where the top of the range is of such high quality, but also everyday food, down to what you find in the local supermarkets,” said José Avillez, a Portuguese chef whose restaurants include the two-star Belcanto in Lisbon.