Dashi is THE fundamental stock used in Japanese cooking, serving as the base for miso soup as well as numerous nimono (simmered) dishes. A simple stock made from kombu (dried kelp) and katsuobushi (dried bonito flakes), dashi preparation is quick and easy, unlike the slow-simmered stocks of Western cooking. Almost every Asian market carries a dried soup base commonly known as "dashinomoto", which work well, but tend to be high in sodium or MSG. I will use the powdered soup base in a pinch, but, to me, dashi is so easy to make that I would rather just make a fresh batch whenever I prepare Japanese food.
Obviously, to make dashi, you will need kombu and katsuobushi, which should be readily available at any Asian market and even at Whole Foods. Since the ingredients are dried, they will have a long shelf life.
The kombu is a thick, leathery seaweed that will usually be coated with what appears to be a layer of dust. Do not remove this layer as it is what lends the dashi its unique, savory flavor (sorry, I hate using the word "umami"). I like to cut the kombu into more manageable pieces (maybe 4-5" long) and store them in a cool pantry.
Kombu sort of looks like a moldy Fruit Roll-Up
Not dust. FLAVOR.
In Japan, the bonito fish is often sold whole and smoked, for the cook to shave themselves. Here, however, the katsuobushi is sold in dried flakes.
Looks a little bit like pencil shavings....
Dashi Stock (ichiban-dashi aka "first stock")
adapted from Just Hungry
1 piece of kombu
1 handful katsuobushi
Filtered cold water
In a small stockpot, soak the kombu in 1 quart of cold water for about 20-30 minutes.
Slowly bring the water and kombu to a boil, then add in the katsuobushi. Immediately turn off the heat, cover, and let stand for 5 minutes.
Strain the dashi through a sieve, pressing all of the liquid through the katsuobushi.
This dashi will last for about 1 week in the refrigerator.
By simply simmering the leftover kombu and katsuobushi with fresh water, you can also make niban dashi (literally, "second stock"); ideal for dishes in which the dashi isn't as primary of an ingredient, or even where a milder flavor is desired.