Niboshi (煮干し) are Japanese dried infant sardines (sometimes incorrectly translated as anchovies). They are one of many varieties of small dried fish used throughout Asia in snacks and as seasoning for soup stocks and other foods.
In Japan, niboshi dashi is one of the more common forms of dashi. It is especially popular as the base stock when making miso soup. Niboshi dashi is made by soaking niboshi in plain water. If left overnight or brought nearly to a boil, the flavor of the small sardines permeates the water and makes a popular stock.
Niboshi are also cooked and served as snacks and as one of the symbolic foods making up the Japanese osechi during New Year. Tazukuri (fried sweet and savory sardines for New Year) are made by frying the dried sardines and then adding a mixture of shoyu, sugar, mirin, and roasted white sesame seeds.