Anybody who has eaten at a Japanese restaurant has almost certainly tasted dried bonito, although without necessarily being aware of it. Dried bonito, or katsuobushi, is one of the three ingredients (the others are water and kombu, or dried sea kelp) used in the basic Japanese soup stock, dashi. The stock takes only minutes to make, unlike classical French and Chinese stocks, which are simmered for hours to extract the flavour from meat, bones and vegetables. Dashi is used in many Japanese steamed or simmered dishes, to make miso soup, in some dipping sauces and in broths for udon and ramen. The delicate shavings are also often used to garnish fried dishes such as agedashi tofu.
Katsuobushi is made by removing the head and internal organs of the bonito, boiling it, smoking it for eight to 10 hours a day for one to two weeks and drying it in the sun. Several times during this process the fish are sprayed with an edible mould that decreases the moisture content of the fish and prevents bacteria growth. The fish becomes as hard as a piece of wood and needs to be shaved on a special, razor-sharp plane similar to the type carpenters use. Traditionally, cooks shaved the katsuobushi on the day it was to be used because it loses its flavour quickly (top chefs shave the bonito just before making dashi). Today, most people opt for the convenience of pre-shaved katsuobushi, which is sold in sealed bags.
To make dashi, wipe a piece of kombu with a damp cloth and put it in a saucepan of cool water over a medium to high heat (Japanese chef Hirohisa Koyama of Basara restaurant in Tokyo recommends using Volvic for its pure flavour). When the water is hot but not simmering, remove the piece of kombu. When the water simmers, add the katsuobushi and remove from the heat. Let the bonito shavings sink to the bottom of the pot and strain the broth through a sieve lined with a piece of slightly damp cheesecloth. The used kombu and katsuobushi retain enough flavour to be simmered again to make another, less refined, dashi broth.
The dashi broth can be flavoured with soy sauce and mirin to make sauces for tempura and cold soba noodles, or spooned over squares of beancurd (garnish with spring onions, grated fresh ginger and more bonito shavings). For miso soup, stir the miso into the dashi, add cubes of soft bean curd and bring to a simmer. Turn off the heat and stir in julienned spring onions.