A turnip is cut across into rounds, each round is slit, and a slice of yellowtail is pushed into the slit. Rice koji is layered over the lot, a weight goes on, and it is left to ferment — a few days in some houses, two or three weeks in others.

There is no vinegar anywhere in it. This is a narezushi, one of the fermented ancestors of the sushi people eat now, and the acidity is produced rather than added. The koji breaks the starch in the rice down, lactic fermentation does the rest, and the sourness and the sweetness both arrive on their own. Cut through a finished piece and you see a narrow dark line of fish between two pale layers of turnip.

It has been made around Kanazawa since the early Edo period. It belongs to winter on this coast, where the sky stays grey for weeks at a time, and it appears on the table at new year. Nothing about it is quick; the turnips have to be in season and the fish has to be in season at the same moment.

Turnip and yellowtail were both seasonal and both expensive once. So the version that spread widely was the other one, made with daikon and dried herring, which anybody could get. This is the same method applied to costlier materials — the technique of a poor household, used on the ingredients of a rich one.