Dashi, a stock from kombu seaweed and bonito flakes, is as essential to Japanese cooking. It is used as a basic ingredient in so many dishes that it has a big influence on the taste of a Japanese meal. It is used in many soups or sauces, including miso soup and tempura sauce. Kikunoi is a famous restaurant from Kyoto with three Michelin stars that has been named after the well from which it draws the water for its dashi. We ate at the Tokyo branch, where they use dashi made from water from the original Kyoto well. That’s how important dashi is.

I had never made my own dashi before, but from now on I always will! The flavor of this dashi was amazing, so much better than any instant dashi I’ve used before. With the temperature control of sous-vide it’s easy to make; the conventional recipe is a bit more involved but that would certainly taste as great. I used the recipe for sous-vide dashi from Modernist Cuisine, page 2-306.

It is best to use freshly-shaved bonito flakes, but that takes skill and a stick of dried bonito is hard to find outside of Japan. So I used commercially prepared and packaged bonito flakes.

Ingredients

For 1 liter (you can make any quantity you like, just calculate the appropriate % of the other ingredients)

1 liter water (use bottled water if tap water is not of very good quality)

25 grams kombu [2.5% by weight]

53 grams bonito flakes [5.3% by weight]

Preparation

Preheat the sous-vide water bath to 60C/140F.

Fill a zip pouch with water of 60C/140F (use an instant-read thermometer).

Cut the kombu into smaller pieces and put them into the zip pouch.

Seal the zip pouch with as little air remaining as possible by submerging it into the water batch (water displacement method).

Cook sous-vide for 1 hour.

Cool in an ice bath and refrigerate for 2 hours (or longer, up to 12 hours, to get a stronger kombu flavor).

Strain. (You can use the kombu again to make ‘secondary dashi’ if you like. This is created by simmering for 20 minutes or so and adding a bit of fresh bonito flakes at the end. Secondary dashi is not as delicate as primary dashi, but for some preparations such as thick soups that is not really a problem.)

Heat the broth to 85C/185F (again, use an instant-read thermometer) and add bonito flakes.

Stir in bonito flakes quickly, and steep for 10 seconds only.

Strain.

The dashi is now ready to be used, or to cool quickly in an ice bath and refrigerate up to 3 days or freeze. Dashi should be used as soon as possible though, because it will lose its special aroma quickly, especially when frozen.