Every year, between April and June, Pacific bonitos migrate. Caught in the warm waters of the Kuroshio, the second largest ocean current in the world after the Gulf Stream, they travel along the west coast of Japan for several thousand kilometers towards the cold and rich waters of Hokkaido. Significantly fattened by the small fish and squids that make this quasi-arctic island famous among humans, they will head back south in the following September. Many will then be caught by fishermen… and transformed into delicious flakes.
To be precise, these flakes called « katsuobushi » are cooked, smoked, and grated bonito fillets. Their role in traditional Japanese cuisine or « washoku » is absolutely crucial: they are what give the primordial broth « dashi » alongside kombu. They are also found in the sprinkle seasonings « furikake » and in a host of delicious sauces, notably the « tsuyu » for cold noodles and the vinegar « tosazu » whose popularity we have seen explode in recent weeks.
Tosazu is a mixture of rice vinegar, soy sauce, and sweet sake infused with smoked bonito flakes. It’s a magical condiment whose ultra-umami taste transforms the most boring leafy vegetables into a refined dish. All roundness and smokiness but never overwhelming, it is unparalleled on an oyster, a ceviche, a tataki, a tuna tartare, a yellowtail sashimi… One could even say that tosazu perfectly illustrates the cardinal principle of great Japanese cuisine: to elevate a fresh ingredient without ever encroaching on its natural perfection.
Such a unique sauce would never have come into being without the know-how of the artisans from Tosa, an ancient prefecture on the Pacific coast of Shikoku from which tosazu gets its name. During their migrations, bonito pass in large numbers off this sunny coastline, known for its temples and citrus fruits. Naturally, the locals have been fishing and preparing them for centuries. Like so many other wonders from Japan, this tosazu that seems so new to us is actually a condiment that has been finely honed over time.
