Dashi is the most foundational ingredient in Japanese cuisine. It is fundamental in producing the umami flavor, which gives Japanese cuisine its signature taste. To produce a high quality dashi is the starting point for all discerning chefs and might be said to make or break the reputation of a high-class chef.
Dashi is a stock made by soaking konbu seaweed (kelp) in water, as its basis, with the most common addition being katsuobushi (dried bonito flakes), but also commonly added are niboshi (dried infant sardines). For shōjin (vegetarian) cuisine dried shiitake mushrooms, as well as roasted soy beans and dried gourd shavings, are used instead of fish. After soaking, these ingredients are removed and the resultant stock is known as dashi.
It is the high percentage of glutamates contained in the konbu, in synergy with the inosinate of the bonito (or guanylate of the shiitake mushrooms), that produces the intense umami flavoring, characteristic of Japanese cuisine.
With just water, konbu and katsuobushi, it is vital therefore that the quality of each ingredient is the best. The high quality and softness of the spring water in Kyoto is one reason its cuisine is said to be so delicious. There are many grades of konbu and the type that is used for making dashi varies according to the chef’s taste and pocket. Bonito flakes are shaved from the fermented and preserved bonito fish, which looks like a lump of wood and is just as hard, which makes it difficult to shave finely. Although shaved bonito flakes are available prepackaged, a good chef will always shave their own flakes using a traditional tool called a kezuriki, which looks just like a plane that a carpenter might use, but the precious flakes are caught in the container beneath the plane.
The first soaking of the ingredients produces ichiban-dashi (first dashi), the most subtle and delicately flavored, which is used for suimono, a clear soup, like consommé, to which other seasonal ingredients can be added. This ichiban-dashi is also used when a light flavor and color are desired, such as chawanmushi. The same ingredients can then be reused to make a stronger flavored stock called niban-dashi (second dashi), which can be used as the basis for miso soup or noodle dipping sauce, etc.
Furthermore, once the konbu has been used for the dashi, it can be made into a delicious pickle called tsukudani (see below for links on how to make).
Professional chefs use an unusual expression for making dashi: dashi wo hiku 出汁を引く, which literally means “to pull the dashi”. This expression refers back to the word “dashi” itself, which literally means “soup that has been taken out from”. The process of making dashi involves first, and most importantly, removing any impurities or scum that float to the surface of the stock in the cooking process that might discolor the liquid and also leave an unpleasant, harsh taste, and then taking out all the steeping ingredients themselves, leaving “the soup from which things have been taken out”. And the verb meaning to take something out is hikidasu 引き出す (literally, to pull and take something out). Can you see the same kanji there that is in the expression dashi wo hiku 出汁を引く? So it’s not so much a matter of pulling the dashi, but rather a shorthand way of expressing the process of removing impurities from the stock, which is vital to the resultant quality of the dashi.