How to Make Dashi from Scratch (Japanese Soup Stock Recipe)
Dashi (出汁) is the savory Japanese soup stock that sits underneath almost everything we cook — miso soup, simmered dishes, noodle broths, tamagoyaki. It’s made from just two humble ingredients: kombu (dried kelp) and katsuobushi (bonito flakes). And while I’ll be the first to admit that most Japanese families reach for a dashi packet on a busy weekday, making dashi from scratch is genuinely easy, takes about fifteen minutes, and the flavor is something special.
This is the classic ichiban dashi (first dashi) — the clean, aromatic stock used for clear soups and miso soup. I’ll walk you through it exactly the way I make it at home, plus how to make a kombu-only vegan version and how to get a second batch (niban dashi) out of the same ingredients. This time I also dropped in a couple of dried shiitake mushrooms with the kombu for a little extra depth — a nice optional addition.
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Why You’ll Love This Recipe
- Just two ingredients. Kombu and bonito flakes — that’s the whole thing.
- Ready in about 15 minutes. No simmering for hours; dashi is fast.
- The real umami backbone. Homemade dashi tastes cleaner and more aromatic than any shortcut.
- Endlessly useful. Miso soup, simmered dishes, noodle broth, tamagoyaki, and more.
What is Dashi?
Dashi is the foundational stock of Japanese cooking. The most common version — awase dashi — combines kombu (dried kelp, which provides glutamate umami) and katsuobushi (dried, shaved bonito, which adds inosinate umami and that smoky aroma). Together they create a savory depth far greater than either alone. Unlike Western stocks that simmer for hours, dashi is quick and delicate: you steep, you strain, you’re done. If you’d rather skip the steeping, my guide to the best dashi packets and powders covers the everyday shortcuts.
Ingredients (Makes about 800ml)
| Ingredient | Amount | Notes |
|---|---|---|
| Water | 1 liter | Soft water is ideal |
| Kombu (dried kelp) | 10 g | A piece roughly 10cm square |
| Katsuobushi (bonito flakes) | 20 g | The thin “hana katsuo” shavings |
That’s it. Quality matters here since there’s nowhere to hide, so it’s worth using good dried kombu and katsuobushi (bonito flakes). I use Hokkaido kombu and bonito flakes made down in Kagoshima — both easy to find online.
How to Make Dashi
Step 1: Soak the Kombu
Wipe the kombu lightly with a dry cloth (don’t wash off the white powder — that’s umami). Cut a couple of slits in it with scissors to help it release flavor, then soak it in the liter of cold water for at least 30 minutes — longer is fine, even a few hours in the fridge. If you want a little extra depth, add a couple of dried shiitake mushrooms to soak alongside the kombu, as I did here.
Step 2: Heat Gently and Remove the Kombu
Put the pot on low-medium heat and bring it slowly toward a simmer. Just before the water reaches a boil — when small bubbles appear around the kombu — take the kombu out. This is the key step: if you let kombu boil hard, the dashi turns cloudy, slimy, and slightly bitter. (Don’t throw that kombu away — see the tip below.)
Save the used kombu. I wrap the spent kombu in plastic and freeze it, and once I’ve collected enough I turn it into kombu no tsukudani (sweet-soy simmered kelp) or homemade shio kombu — nothing wasted.
Step 3: Add the Bonito Flakes
Bring the water to a brief boil, then add the katsuobushi all at once. Turn off the heat (or lower it right down) and let the flakes steep for about 1–2 minutes. Don’t stir much — just let them sink naturally. Over-boiling the bonito makes the dashi harsh and fishy instead of clean and aromatic.
Step 4: Strain
Line a sieve with a paper towel or fine cloth set over a bowl, and pour the dashi through. Let it drip naturally — don’t press or squeeze the flakes, or you’ll push bitterness into the stock. What comes through is a clear, golden, deeply savory ichiban dashi, ready to use.
Variations
Kombu-Only Dashi (Vegan)
For a vegan dashi, simply skip the bonito: soak kombu in water, warm gently, and remove it before boiling. It’s milder and cleaner. For more depth, add a few dried shiitake mushrooms to the soak — kombu plus shiitake makes a lovely plant-based stock. I cover this more in my guide to dashi substitutes.
Niban Dashi (Second Dashi)
Don’t throw away the used kombu and bonito — you can make a second, milder niban dashi. Put them back in a pot with about 500ml fresh water, simmer gently for around 10 minutes, add a small handful of fresh flakes if you like, then strain. It’s not as refined as the first dashi, but it’s perfect for simmered dishes and everyday miso soup — nothing wasted. I used my niban dashi to make miso soup that same evening (pictured below).
How to Use Your Dashi
- Make the everyday miso soup Japanese people actually make.
- Use it as the base for simmered dishes (nimono), oyakodon, and gyudon.
- Add it to dashi tamagoyaki for a juicy rolled omelette.
Storing Dashi
Fresh dashi is best used the day you make it, but it keeps in the fridge for 2–3 days in a sealed container. It also freezes well — freeze it in an ice cube tray, then keep the cubes in a bag and drop them straight into soups and simmers as needed. Making a big batch and freezing it is a great way to have real homemade dashi on hand without the daily effort.
Frequently Asked Questions
Can I make dashi with just bonito flakes (no kombu)?
Yes. Bring water to a boil, add bonito flakes, steep briefly off the heat, and strain. It’ll be smoky and savory, just without the rounded glutamate depth kombu adds. Conversely, you can also make dashi with just kombu for a mild, vegan stock.
Why shouldn’t I boil the kombu?
Boiling kombu hard releases sliminess and a bitter, overly strong seaweed flavor, and makes the dashi cloudy. Remove the kombu just before the water boils to keep the stock clear and clean-tasting.
Is homemade dashi worth it over a packet?
For a special soup or when you want the cleanest flavor, yes — homemade ichiban dashi is noticeably more aromatic. For busy weeknights, a good dashi packet or powder is completely fine and what most Japanese families use day to day. It’s nice to know how to do both.
Dashi (Japanese Soup Stock)
Ingredients
Method
- Wipe the kombu with a dry cloth (don’t wash off the white umami powder). Cut a couple of slits in it and soak in the litre of cold water for at least 30 minutes.
- Heat the pot gently toward a simmer. Just before it boils, when small bubbles appear around the kombu, remove the kombu.
- Bring to a brief boil, add the katsuobushi all at once, then turn off the heat and let the flakes steep for 1-2 minutes.
- Strain through a paper-towel-lined sieve set over a bowl. Let it drip naturally without pressing the flakes. Use the clear golden dashi right away, or store.
