What Is Dashi?

If soy sauce is the most visible building block of Japanese flavour, dashi is the invisible one. It is a light, clean stock — most commonly made from dried kombu (kelp) and katsuobushi (bonito flakes) — that forms the base of miso soup, noodle broths, simmered dishes, sauces, and more. Unlike Western stocks that cook for hours, dashi is made in minutes. Its flavour is subtle, clean, and profoundly savoury — the essence of umami.

There are several types of dashi suited to different dishes and dietary requirements. Here are three you should know.

1. Ichiban Dashi (一番だし) — Classic First Dashi

Ichiban means "first" — this is dashi made from the first infusion of kombu and katsuobushi, resulting in the most delicate and aromatic stock. Use it for clear soups and dishes where the dashi flavour will shine.

Ingredients

  • 1 litre cold water
  • 15g dried kombu
  • 20g katsuobushi (bonito flakes)

Method

  1. Place the kombu in cold water and leave to soak for at least 30 minutes (or up to several hours in the fridge for a gentler extraction).
  2. Place the pot over medium-low heat. As the water slowly heats, the kombu will release its glutamates into the liquid. Remove the kombu just before the water reaches a simmer — around 60°C. Do not boil kombu, as this makes the stock bitter and slimy.
  3. Bring the liquid to a gentle simmer, then add the katsuobushi all at once.
  4. Turn off the heat immediately. Let the flakes steep for 3–5 minutes — do not stir.
  5. Strain through a fine mesh sieve lined with a cloth or kitchen paper. Do not squeeze the flakes; just let them drain naturally.

The resulting dashi is pale golden, clean, and faintly smoky. Use it immediately or refrigerate for up to 3 days.

2. Kombu Dashi — Vegan & Vegetarian Stock

For a plant-based alternative, kombu dashi is an excellent option. It has a gentler, more oceanic flavour than ichiban dashi and works well in miso soup, vegetable simmered dishes, and as a base for vegetarian ramen.

Method

  1. Soak 15g of kombu in 1 litre of cold water for a minimum of 30 minutes, ideally 1–2 hours.
  2. For a cold-brew version (best flavour): refrigerate the kombu and water overnight. Strain and use cold or gently warmed.
  3. For a hot version: heat gently to just below simmering, hold at that temperature for 10 minutes, then remove the kombu and strain.

3. Shiitake Dashi — Deep Umami for Simmered Dishes

Dried shiitake mushrooms produce a rich, earthy stock with a powerful umami punch. It's often combined with kombu dashi for a well-rounded vegan stock.

Method

  1. Soak 4–6 dried shiitake mushrooms in 1 litre of cold water for at least 2 hours, or overnight in the fridge.
  2. Remove the mushrooms (they can be sliced and used in your dish) and gently heat the liquid if needed.
  3. Do not boil — keep the heat moderate to preserve the delicate flavour compounds.

Tips for Better Dashi

  • Use good kombu: Look for Rishiri or Hidaka kombu from Hokkaido — widely considered the finest varieties.
  • Don't wash kombu: The white powder on the surface (mannitol) contributes to the umami flavour. Just wipe gently with a damp cloth if needed.
  • Temperature matters: Both kombu and bonito release the best flavour at moderate temperatures. Boiling degrades quality.
  • Save the second dashi: The strained kombu and bonito flakes can be simmered again to make niban dashi (second dashi) — less refined, but perfect for hearty simmered dishes.

How to Use Dashi

Once you have a batch of dashi, the possibilities are wide open:

  • Dissolve miso paste into warm dashi for miso soup
  • Use as a base for udon or soba broth
  • Make chawanmushi (savoury egg custard) with dashi, eggs, and soy
  • Use in simmered vegetable dishes (nimono)
  • Deglaze pans for quick sauces with soy and mirin

Once you understand dashi, a whole dimension of Japanese cooking becomes accessible. It takes almost no active effort and rewards you with flavour that instant stock simply cannot replicate.