Ingredients

   
10g kombu (dried kelp)
20g katsuobushi (bonito flakes)
1000g water

Steps

  1. Combine kombu and water in a pot. Soak at least 30 minutes until kombu softens.

  2. Heat over very low heat. When small bubbles appear at the edges (just before boiling), remove kombu.

  3. Bring to a brief boil, then turn off heat. Add bonito flakes. Let steep undisturbed for about 30 seconds until flakes are saturated and begin to sink.

  4. Strain through a fine-mesh sieve lined with cheesecloth or a paper towel. Do not squeeze the bonito — let it drain naturally.

Notes

  • The ratio is 1% kombu and 2% bonito by weight of water. Scale freely.
  • Do not boil the kombu — it releases slime and bitterness. Remove just before the water boils.
  • Do not squeeze the bonito flakes — squeezing extracts bitter compounds and clouds the dashi.
  • This is ichiban dashi (first brew) — the most refined, cleanest flavor. Use for clear soups, chawanmushi, and dishes where dashi is the star.
  • Save the used kombu and bonito. Add them to 800g fresh water, simmer 10 minutes, and strain for niban dashi (second brew) — weaker but good for miso soup and simmered dishes.
  • Keeps refrigerated 3 days, frozen 1 month.