Vinegared Sardines (Tosazu)

Learn a new Japanese sardine recipe from Chef Isao Yamada involving marinating the sardines in tosazu, a Tosa vinegar-based marinade infused with bonito for a flavorful and umami-rich dish. The method for preparing tosazu and the step-by-step process for marinating the sardines are provided in the article.

Here's another method for sardines, thanks to Chef Isao Yamada: Marinate them in vinegar. In my last post I mentioned I wanted to learn more Japanese sardine preparations, to give me some options for this flavorful but underappreciated fish (at least in America). Yamada san reeled a bunch of possibilities, including nimono (last post), tempura, grilled, raw and vinegared (sunomono).

We decided to marinate sardine fillets in tosazu, which means "Tosa vinegar." Tosa is the ancient name for an area in Shikoku (one of Japan's main islands), a place where fishermen have long pulled in bonito (katsuo) -- so the name suggests an infusion of katsuobushi, that is, dried shaved bonito. Small word, lots of meaning. The bonito adds a heady dose of smoke, flavor, and rich umami to the sardines. Combine this with the acidity of the vinegar, and you have a delicious, complex preparation that's quite simple to prepare. First, here's the method for preparing the tosazu:

1 cup dashi
3 tablespoons mirin
1/2 cup Japanese rice vinegar
1 (3 inch) piece of kombu
3 tablespoons soy sauce
1 tablespoon usukuchi soy sauce (saltier, lighter color soy sauce)
1 small handful of katuobushi (dried, shaved bonito)

Place the dashi, mirin, rice vinegar and soy sauce in a saucepan and bring to a boil over medium heat. Boil for two minutes and add the both kinds of soy sauce. Boil for 30 seconds more. Turn off the heat, add the handful of katsuobushi, and let it steep for 5 minutes. Strain the liquid through a cheesecloth, allow to cool, and you have your tosazu. Set aside.

Before I go on, let me interject with a couple of notes (but of course): You want the sweetness of the mirin to balance the acidity of the vinegar and savoriness of the soy sauce. Taste the tosazu to see if you're getting that. Also, tossing in the handful of dried, shaved bonito is called oigatsuo -- "chasing" katsuo, a technique to amp up umami. Finally, as with nimono, we're creating supercharged water to infuse flavor in an ingredient, classic Japanese cooking at work. Okay, back to our regularly scheduled technique:

6 fresh sardine fillets
Salt for salting
2 tablespoons tosazu
2 tablespoons water
1 teaspoon sugar
1 tablespoon hari shoga, ginger sliced into thin needles
5 shiso leaves, sliced as thinly as possible
1 tablespoon myoga, thinly sliced (optional)
Sesame seeds

Lightly salt the sardine fillets and place, skin side down, on a plate. Allow the fish to cure for 20 minutes in the refrigerator. Meanwhile, combine the tosazu, water and sugar in a bowl. When the sardines are ready, rinse off the salt. Place them in the bowl with the tosazu and marinate for 5 minutes. (Up the proportions of liquid, if necessary, to cover the fillets completely.) When the fillets are ready, use your fingernail to get under the skin and pull it off. Thinly slice the sardines on an angle. Assemble the dish by piling the sardines in a bowl, pouring in a little tosazu, and topping with ginger, shiso, myoga and a sprinkle of sesame seeds. Enjoy.

(By the way, tosazu can sit in the fridge for a while. I'll be back with more uses for this ingredient in future posts.)