Good dashi smells like the sea on a calm morning: briny, faintly smoky, with a warmth that hits somewhere deep. It’s the invisible backbone of Japanese cuisine, present in everything from a humble bowl of homemade miso soup to noodle shop udon or soba, to the most refined kaiseki meals. Without good dashi, even carefully prepared Japanese food tastes flat.
I’ve been making homemade dashi for over three decades now, and the ritual never gets old. There’s something meditative about watching the simple broth come together from just two ingredients: kombu and katsuobushi .
What surprises most people is how fast this dashi recipe comes together. We’re talking four minutes of actual cooking time (though you do need to plan ahead to soak the kombu overnight). This Japanese dashi recipe follows a method I picked up from a chef in Kyoto who insisted that proper extraction requires restraint. You don’t boil the kombu or simmer the katsuobushi. You coax the flavor out gently, and the result is a broth so clean and balanced you’ll want to drink it straight from the pot.
The science is straightforward: kombu delivers glutamates while katsuobushi contributes inosinates. Together, these compounds create a synergistic effect that amplifies umami far beyond what either ingredient provides alone. Once you’ve tasted the difference, there’s no going back.
- Why My Recipe Works
- Key Ingredients and Why They Matter
- PREP NOTES
- HOW TO MAKE DASHI
- WHAT TO WATCH FOR
- STORAGE AND REHEATING
- HOW TO USE DASHI
- VARIATIONS
- 📖 Recipe
- FAQ
- Comments
Why My Recipe Works
- Cold-extracting the kombu prevents sliminess. Boiling kelp releases mucilaginous compounds that make dashi viscous and cloudy. Soaking it overnight in cold water pulls out the glutamates you want while leaving the undesirable textures behind.
- Cutting the heat before adding katsuobushi avoids bitterness. The smoking process that creates katsuobushi leaves behind compounds that turn harsh when boiled. By bringing the kombu dashi to a boil and then turning off the heat, you extract the clean, smoky flavor without the acrid notes.
- The short steep is intentional. Going longer than 3-4 minutes doesn’t mean more flavor. The inosinates in bonito flakes release quickly, and extended contact starts pulling tannins and other harsh compounds.
- Kombu and katsuobushi create synergistic umami. Glutamates (from kombu) and inosinates (from bonito) amplify each other’s effect on your taste receptors. This is why traditional dashi uses both, and why the combination tastes far more savory than the sum of its parts.
Key Ingredients and Why They Matter
- Kombu (Dried Kelp): The source of glutamic acids that give dashi its foundational umami. Different varieties produce different results: Rishiri kombu makes clear, refined dashi; Rausu kombu produces darker, more intensely savory stock that’s almost meaty. Ma-kombu is the workhorse, reliable and versatile. By the way, that whitish powder on the surface is not mold; it’s a combination of dried salt, glutamate, and mannitol, and there’s no need to remove it.
- Katsuobushi (Dried “Bonito” Flakes): Although it’s often labeled as “bonito flakes”, Katsuobushi is actually made from skipjack tuna. The fish is filleted and then cooked, dried, smoked, and often fermented. The flakes contribute inosinates, another umami compound, plus a distinct smoky depth. Pre-shaved hanakatsuo works well for everyday dashi. For special occasions, true hon-karebushi (fermented katsuobushi shaved fresh) produces noticeably more refined flavor.
- Water: Quality matters here because dashi is mostly water. Filtered water with neutral flavor lets the kombu and katsuobushi shine. Heavily chlorinated tap water can interfere with the delicate extraction.
Substitutions
- If you can’t find katsuobushi or want vegan dashi: Dried shiitake mushrooms create a vegetarian alternative, though the flavor profile shifts significantly toward earthy mushroom rather than oceanic. You can extract the dashi by soaking a few of them together with kombu in cold water overnight.
- For a stronger, fish-forward dashi: Add niboshi (dried baby anchovies) or iriko . This is common on the island of Shikoku and works well for hearty dishes like udon broth.
- In a pinch: Dashi packs (pre-portioned sachets of kombu and katsuobushi) bridge the gap between instant granules and from-scratch. Kayanoya makes excellent ones. Avoid instant dashi granules if you can; they’re mostly MSG and flavorings.
PREP NOTES
- Kombu soak: Minimum 3 hours, ideally overnight. I usually put the kombu in a water bottle or jar in the fridge before bed.
- Water temperature: Start with cold water for the soak. The extraction happens slowly in the fridge.
- Katsuobushi measurement: About 15 grams per 4 cups of water. If you don’t have a scale, that’s roughly one loose handful.
- Don’t rinse the kombu: That white powder is flavor. Just wipe off any visible debris with a damp cloth if needed.
HOW TO MAKE DASHI
Making dashi is less about cooking and more about extraction. You’re pulling specific flavor compounds from two ingredients at the right temperatures for the right amount of time. Rush it or overheat it, and you’ll end up with something murky and harsh instead of clean and aromatic.
Stage 1: Cold-Extract the Kombu
Add your kombu to cold water and refrigerate for at least 3 hours, preferably overnight. I usually do this in a water bottle or carafe because it’s easier to store, but a bowl or even the pot you plan to cook in works fine. The kombu will soften and release glutamates slowly into the water, creating what’s called kombu dashi. You can use this plant-based stock on its own for vegetarian dishes.
💡 TIP: If you’re short on time, you can warm the water with the kombu over low heat for about 10 minutes instead of cold-soaking. Remove the kombu just before the water starts to simmer. The results won’t be quite as clean, but it works.
Stage 2: Heat and Remove
Take the kombu out of the water and set it aside (you can use it for tsukudani or add it to simmered dishes). Bring the konbu dashi to a boil over medium-high heat.
🧪 SCIENCE: Kombu releases a mucilaginous compound when heated past about 140°F (60°C). If you leave it in while bringing the water to a boil, your dashi will turn slimy and cloudy. Cold extraction bypasses this problem entirely.
Stage 3: Add Katsuobushi and Steep
The moment your dashi reaches a boil, turn off the heat completely. Add the katsuobushi and let it steep undisturbed for 3-4 minutes. You’ll see the flakes absorb water and slowly sink to the bottom.
💡 TIP: Don’t stir or press on the flakes. Just let them do their thing. Agitation extracts harsher flavors.
Stage 4: Strain and Use
Pour the dashi through a fine-mesh strainer lined with cheesecloth or a paper towel if you want crystal-clear results. The plain strainer works fine for everyday cooking. Use the dashi immediately, or let it cool completely before refrigerating. It keeps for about 3 days in the fridge.
WHAT TO WATCH FOR
- Cloudy or slimy dashi: You left the kombu in too long while heating, or you boiled it. Next time, remove the kombu before the water reaches a simmer, or stick to cold extraction.
- Bitter or harsh flavor: The katsuobushi was steeped too long or in water that was too hot. Steep for no more than 4 minutes, and always cut the heat before adding the flakes.
- Weak, flat taste: Either your kombu didn’t soak long enough (give it the full overnight), or your ingredients are old. Kombu and katsuobushi lose potency over time. Check that your kombu still has that whitish powder and your katsuobushi is soft and pliable with a distinctly smoky aroma.
- Fishy off-flavors: Could be old katsuobushi or low-quality flakes made with a different fish. Check the ingredient label; it should only list “skipjack tuna” or “bonito”.
STORAGE AND REHEATING
- Refrigerator: Store in an airtight container for up to 3 days. The flavor diminishes over time, so use it sooner rather than later.
- Freezer: Freeze in ice cube trays or small containers to make it easy to portion and keep them for up to 1 month. Any longer and it may start to taste freezer burned.
- Reheating: Warm gently over low heat. Don’t boil it again; high heat degrades the delicate flavor compounds you worked to preserve.
- The spent kombu: Refrigerate for up to a week and use in simmered dishes, or slice thin and make tsukudani (soy-braised kelp).
- The spent katsuobushi: Can be dried out and used to make furikake , though most people discard it.
HOW TO USE DASHI
Once you have homemade dashi, you’ve unlocked a huge variety of Japanese dishes you can make at home. The clean umami of the dashi melds with the fermented complexity of miso paste to make miso soup . For a quick weeknight meal, use your dashi as the base for kitsune udon with its sweet simmered tofu, or go richer with shoyu ramen . Egg dishes like chawanmushi (silky Japanese steamed custard) showcase dashi’s subtle character beautifully. And if you want to see what good dashi can do for a simple weekday meal, try it in gyudon (beef bowl) or oyakodon (chicken & rice bowl) for an easy one-pan meal that comes together in minutes.
VARIATIONS
- Vegetarian Kombu Dashi: Skip the katsuobushi and use only the cold-extracted kombu water. Soak dried shiitake mushrooms with the kombu for additional depth. This works well for shojin ryori (Buddhist temple cuisine) and vegan Japanese cooking.
- Iriko Dashi: Replace katsuobushi with niboshi (dried baby anchovies) for a stronger, fishier stock.
- Awase Dashi: Combine multiple umami sources: kombu, katsuobushi, and a dried shiitake. This layered approach creates exceptionally complex dashi for special dishes.
- Quick Dashi (Emergency Method): Heat kombu and water together over low heat for 10 minutes (don’t let it boil), remove the kombu before it starts simmering. Add katsuobushi and steep for 3-4 minutes. Not as refined, but far better than instant.
📖 Recipe
Equipment
Units
Ingredients1x2x3x
- 4 ¼ cups water
- 10 grams konbu
- 15 grams katsuobushi
Instructions
- Add the 10 grams konbu to the 4 ¼ cups water and soak for at least 3 hours. You can store this konbu dashi in a refrigerator for up to 3 days.
- Remove the konbu and bring the dashi to a boil (you can use the konbu for something else).
- Turn off the heat, and add the 15 grams katsuobushi . Let this steep for 3-4 minutes.
- Strain the dashi and use it right away, or let it cool completely and store it in the refrigerator.
Nutrition Facts
Traditional dashi is made from just three ingredients: kombu (dried kelp), katsuobushi (dried bonito flakes). The kombu provides glutamate while the bonito (a.k.a. skipjack tuna) adds inosinate. Together, these compounds create synergistic umami, the savory depth that defines Japanese cuisine. Variations exist using shiitake mushrooms, dried anchovies, or other dried fish, depending on the region and dish.
You don’t actually boil dashi, and this is where many home cooks go wrong. Heat the kombu water until just before it boils, remove the kombu, then turn off the heat completely before adding katsuobushi. The flakes steep in hot (not boiling) water for 3-4 minutes. Boiling can make dashi bitter, fishy, or slimy.
Scale the standard recipe proportionally: use about 2.5 grams kombu and 4 grams katsuobushi per cup (240ml) of water.
Your best substitutes in order of quality: dashi packs (pre-portioned sachets of kombu and katsuobushi), mushroom broth for vegetarian dishes, or light chicken stock in a pinch. Instant dashi granules work but taste noticeably artificial. For the most authentic flavor, there’s no real substitute for making it fresh.
Refrigerated in an airtight container, homemade dashi keeps for about 3 days. You can freeze it for up to a month. For best results, make dashi fresh when you need it; the whole process only takes a few minutes of active cooking.
Dashi is the traditional Japanese soup stock made by extracting flavor from kombu and katsuobushi. Hondashi is a brand of instant dashi granules, essentially MSG and flavorings designed to approximate dashi’s taste. While hondashi is convenient and widely used, it lacks the clean, nuanced flavor of properly made dashi from scratch.
Dashi (Japanese Soup Stock)
Equipment
- Medium Glass Bowl
- small stainless saucepan
- Fine Mesh Strainer
Ingredients
- 4 ¼ cups water
- 10 grams konbu
- 15 grams katsuobushi
Instructions
- Add the 10 grams konbu to the 4 ¼ cups water and soak for at least 3 hours. You can store this konbu dashi in a refrigerator for up to 3 days. 4 ¼ cups water, 10 grams konbu
- Remove the konbu and bring the dashi to a boil (you can use the konbu for something else).
- Turn off the heat, and add the 15 grams katsuobushi . Let this steep for 3-4 minutes. 15 grams katsuobushi
- Strain the dashi and use it right away, or let it cool completely and store it in the refrigerator.
