As steam began to rise from my pot, I plucked the glistening strands of kombu from the hot water and set them aside.
Behind the Recipes
Homemade Dashi is the Soul of Japanese Cooking
Dashi, the backbone of countless soups, stews, and sauces, is the cuisine’s universal, umami-rich elixir.
By Published Apr. 2, 2024.
I pulled the pot from the heat, added a handful of katsuobushi to the water, and watched the translucent fish flakes slowly sink beneath the surface. Minutes later, I poured the mix through a fine-mesh strainer to remove the fish, yielding a batch of elegantly perfumed, light golden dashi.
That simplicity is extraordinary among stocks, since many styles require loads of meat or vegetables plus hours of simmering and skimming to achieve depth and clarity.
But with awase dashi, Japan’s ubiquitous stock made with kombu (dried kelp) and katsuobushi (dried, smoked, fermented, and shaved skipjack tuna flakes), it takes the barest effort to produce a limpid, savory elixir that’s delicately smoky and rich with the taste of the ocean. (There are multiple styles of dashi; “awase dashi” is the formal name for the most common style. The word “dashi” is derived from the verb “dasu,” meaning “to extract”).
Many cooks compare the preparation to brewing tea: Steep the kombu and katsuobushi in water, then strain.
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Dashi is the heartbeat of Japanese cooking. We think of [it] as a seasoning, not just as a soup or broth.
Science: Brew Pitch-Perfect Dashi in Three Simple Steps
Nailing dashi’s balance of clean, oceanic savor and smoky backbone is all about extracting the abundant umami-rich compounds found in kombu and katsuobushi—and avoiding the ones that taste unpleasantly bitter or fishy. Here’s our carefully calibrated method.
- Cold-steep the Kombu: Soaking kombu in cold water initiates the extraction of glutamic and other amino acids and fragrant aldehydes. Capping the soak time at 8 hours prevents the extraction of polysaccharides that would make the kombu perceptibly slimy in the dashi.
- Hot-Steep the Kombu: Slowly heating the kombu and its soaking liquid to 150 degrees (when the water is steaming) further extracts the good-tasting compounds and avoids over-extraction of the kelp, which happens at higher temperatures and leads to bitterness.
- Hot-Steep the Katsuobushi: Bringing the liquid (strained of kombu) to 200 degrees and adding the katsuobushi for a 3-minute steep draws out rich, smooth savor and smokiness that beautifully balance the clean, saline sweetness of the seaweed.
Because kombu and katsuobushi are meticulously crafted according to age-old processes that deeply concentrate their taste and aroma, it takes minimal time and effort to suffuse the water with their savor.
Plus, the seaweed and fish are a dynamic pair: Each is chock-full of savory substances that synergize when they meet, so the stock’s umami depth magnifies exponentially. Its flavor, which manages to be both distinct and subtle, can stand out in a preparation like miso soup or quietly accentuate the savoriness of innumerable other dishes throughout Japanese cuisine.
Katsuobushi
Looking at a pile of diaphanous katsuobushi, you’d never guess that the flakes were shaved from a piece of dried fish as hard and dense as wood—or that the rigid fillet was made from a creature that once swam in the ocean.
But it’s precisely that transformation from raw fish to papery flakes that demonstrates the complex undertaking behind one of Japan’s most revered ingredients.
Most katsuobushi (commonly called bonito flakes, because the skipjack tuna they’re made from is vernacularly known as bonito) is produced in Yaizu, the coastal city in Japan’s Shizuoka Prefecture. The process varies by producer, but it starts with simmering the fillets to firm them up and multiply their stores of available inosinate, one of the key substances behind katsuobushi’s umami depth.
Then, the fish is repeatedly wood-smoked and cooled over the course of about a month, which infuses it with rich aroma and evaporates so much of its water that it hardens. Sometimes it’s sold at this stage, but often it’s inoculated with mold to create a higher-grade katsuobushi loaded with complexity and marine sweetness—qualities that reveal themselves when the fish is shaved into the pink wisps that “dance” over rice or okonomiyaki or collapse into a pot of dashi.
Kombu
Kombu isn’t just one of the world’s richest natural sources of umami; it’s the birthplace of the taste and the term. Intrigued by the inexplicably savory depth in kombu dashi, Japanese chemist Kikunae Ikeda analyzed the inky-brown kelp in the early 1900s, isolating various chemical constituents of kombu and discovering that its deep savor was due to an amino acid salt called glutamate.
He named the distinctive flavor “umami” (roughly, “delicious taste”), noting how it lingers on the palate and magnifies the flavors of everything around it. (Ikeda subsequently developed a method to manufacture monosodium glutamate [MSG] crystals in large quantities for use as a ubiquitous seasoning and flavor enhancer.)
“Throw kombu in anything, and [the food] will get better in flavor,” cookbook author and cooking teacher Sonoko Sakai told me. “It’s such a beautiful aroma. It’s almost restorative.”
Producers tap into that aromatic savor by harvesting the top portion of the long plant, which is cultivated mostly in the cold waters off Hokkaido—and increasingly along the northern United States coastline—and then sun-drying the fronds and compressing them to release more moisture. Depending on the variety, the kombu might then be cured for a year or more to further refine its flavor and aroma.
“We think of dashi as a seasoning, not just as a soup or broth,” said renowned California-based cookbook author and cooking teacher Sonoko Sakai, noting that she considers it “the heartbeat of Japanese cooking.”
Sakai, who as a child lived with her grandmother in Kamakura, just south of Tokyo, described the painstaking way her grandmother would hover over a batch: “She would lower her glasses and really pay attention to the moment the kombu should be plucked out,” Sakai said. “It was quite an art.”
The Magic of Miso Soup
“Miso soup is considered by Japanese people to be the best Japanese food,” Mamiko Nishiyama told me when we spoke about the dish, one of the most common uses for dashi. Nishiyama, who owns Yagicho Honten, Tokyo’s centuries-old shop that specializes in dashi ingredients, stressed the importance of the soup’s aroma—a combination of saline-smoky dashi and the funky, sour, salty sweetness of miso that should “spread around you the moment you open the lid off the bowl.”
With Kombu, The Right Temperature Matters
Besides using ample amounts of good‑quality kombu and katsuobushi to infuse the water (1 ounce of each per 4 cups of resulting broth is common), steeping time and temperature are the only variables to mind. Many cooks steep the kombu in cold water, then in hot water; strain it out and steep the katsuobushi in the kombu-infused liquid; and then strain out the fish flakes.
Cold-steeping the kombu starts to extract the seaweed’s favorable compounds (1 to 8 hours led to an extraction full of clean, sweet, saline depth), while the hot steep draws out compounds that are soluble at higher temperatures.
After the cold steep, warming the pot over medium-low heat to 150 degrees finished the job nicely, maximizing the kombu’s steep time before the water became too hot. As for the katsuobushi, I ran several tests and discovered that its sweet spot was a 3-minute steep in 200-degree water. The dashi tasted complex and balanced without the distraction of off-flavors.
With a pitch-perfect pot of dashi in hand, miso soup is just minutes away.
