How To Make Kombu Broth (Vegetarian Dashi)

Kombu broth, or dashi, is as quintessential to Japanese cooking as chicken broth is to American cooks. The ingredients are incredibly simple, and the technique for making dashi is much easier than any other broth you can make.

Kombu Is the Key

Japanese dashi is always made with kombu, which is a dried kelp full of glutamic acids. The kombu gives dashi and every dish made from it a rich umami flavor. Kombu can be found at Asian markets and some chain grocery stores. Look for kombu with plenty of the cloudy white crystals over the surface.

A Hybridized Method

Many recipes for dashi insist that kombu should never be boiled, claiming that it will become bitter or slimy.

Truthfully, Japanese cooks make two primary versions of dashi. The first is incredibly delicate and gently simmers the kombu without bringing it to a boil; a second dashi can be made from the same piece of kombu, and this second dashi is boiled for as long as 20 minutes.

The recipe below calls for a hybrid of the two methods. Soaking the kombu overnight releases almost all of the kombu's flavor without concentrating it, while bringing the kombu water to a boil releases some of the kombu's thickening power. The result is a heartier kombu broth, perfect for vegetarian soups.

Learn more: Ingredient Spotlight: Dried Kombu

For Vegetarian Dashi: Mushrooms, Not Bonito

Another primary ingredient for traditional dashi is dried bonito. Bonito is a dried fish which can be found whole (mostly in Japan) or in flake form, and it provides a ton of salty, earthy flavor for dashi — but it is not vegan- or vegetarian-friendly.

You could simply leave out the bonito and make a true kombu broth, or you can replace the bonito with something equally savory and earthy — like dried shiitake mushrooms. A bonus of using dried mushrooms for making kombu broth is that the mushrooms can be eaten after making the broth. Chop them and add them to miso soup, stir-fries, or even pasta.

Learn more: Why Dried Shiitake Mushrooms Should Be in Your Pantry

Using Kombu Broth in Vegetarian Miso Soup

This vegetarian kombu broth was designed to turn simple miso soup — often served as a side dish — into a stand-alone meal. Save the mushrooms from making this broth and add them with savory red miso and silken tofu to make a richer, heartier version of miso soup.

Vegetarian miso soup: How To Make Miso Soup: The Best Method for Most Home Cooks

And for those who'd prefer to a lighter soup, but still want to keep things vegetarian, use this broth with a combinations of white and yellow miso in classic miso soup.

Classic miso soup: How To Make Miso Soup

Soak the kombu: Combine the water and kombu in a 1-quart or larger saucepan and soak the kombu for at least 8 hours or overnight.