Niboshi are dried sardines which are used in Japanese cooking. There are a number of uses for niboshi, ranging from snack foods to soup stocks, and they are abundant at Asian markets. You may also hear “niboshi” translated as “anchovies.” This is technically incorrect; although niboshi are small, like anchovies, they are really baby sardines, an entirely different fish. If you have trouble finding niboshi in your area, you can also purchase the fish through companies which produce it.
One of the most common uses for niboshi is in a soup stock called dashi. Dashi is often mixed with miso to make miso soup, and it forms a base stock for a variety of other dishes as well. To make dashi, people soak niboshi in water and then bring the water to a simmer to release the intense flavor of these fish. The broth is strained before use to remove the fish. Some companies make a form of instant dashi with powdered niboshi and other ingredients.
Because these fish have such an intense, concentrated flavor, they are also used to flavor various Japanese dishes. Some people add strong dashi stock to various foods for a fishy flavor, or they use chopped and soaked niboshi. The use of various preserved fish is common in many branches of Asian cuisine; you can also find ingredients like fish paste and fish sauce which also create a concentrated fish flavor.
In some parts of Japan, niboshi are also eaten as a snack food. They are typically fried and rolled in seasonings, and they may be dipped in an assortment of sauces. This snack food is common in street stalls, and it can sometimes be found packaged in Japanese markets. Niboshi can also be used to garnish dishes once they have been finished; some people enjoy the texture and flavor of plain dried niboshi.
You may see a lot of niboshi around the lunar new year, when niboshi snacks are especially popular. If you want to prepare dishes with niboshi at home, you can find the dried fish product pre-packaged in some markets, or available in bulk in others. Keep the fish in a cool dry place out of the light until you use it, and if you only use part of a package, seal the rest up in an airtight container so that the niboshi do not become stale or get moist.