Old-School Miso Soup, Everything You Ever Wanted to Know Recipe

A collage showing the steps to making homemade miso soup.

While doing research for his book The Story of Sushi, author Trevor Corson discovered that soy sauce originated as a byproduct of miso. Who knew? Miso-obsessed, Corson wanted to learn more about the traditional fermentation process, so he visited a miso-making factory, then tracked down old-school miso ingredients to make his own at home. We asked him to document. Thanks, Trevor!

Words and Photographs by Trevor Corson | During the three years I lived in Japan, I ate a lot of miso soup, but I never knew what it was. I just figured it was extracted from, you know, a miso plant, or maybe the miso bird, a Japanese relative of the chicken. The Japanese people around me treated miso like a god, so I knew it was special, maybe even magical, and whenever I visited a Buddhist temple or Shinto shrine, it seemed possible that lurking in the shadows among the statues of fox spirits and the bundles of sacred straw there might be a statue or likeness of a miso. Never saw one.

Not until I wrote an entire book related to Japanese cuisine did I learn the secrets of what the Japanese call misoshiru, or miso soup. Now the tables have turned. I've morphed into an obnoxious miso-soup purist. I won't touch those convenient packs of instant mix, nor will I buy standard miso at a standard store. When it's time to make the soup in my New York kitchen, I bow before the altar of authenticity, don the robes of a Zen master (metaphorically speaking) and practice the ancient art of the miso soup Nazi—hey, the Japanese had fascism, too. Watch me make it from scratch, after the jump.

Miso Soup Starts With Seaweed

Dried kelp soaking in a pot of water with a package of dried kelp on the counter next to the cooktop.

Dried kelp, or konbu.

True miso soup, it turns out, starts not with miso at all, but with seaweed. As Japanese food aficionados know, the basic broth that serves as the foundation for most Japanese cooking, including miso soup, is called dashi. To make dashi, you drop sheets of crackly dried kelp into cold water. For a large batch, I use about eight cups of water and 5 to 7 broken-up sheets of dried kelp, called konbu in Japanese. Turn the heat on medium and hang around the kitchen, keeping an eye on things. You want to bring the water to the cusp of boiling, without letting it actually boil. This takes a while.

Conventional wisdom says you never want the water to boil when you're making miso soup. Most Japanese cooks believe the kelp releases bitter compounds if the water boils, although other chefs don’t think it's a problem. Later, after you add the miso, boiling water will almost certainly kill the active enzymes in live miso that add taste and benefits to your health. This, I believe, will anger the god of miso.

Kelp Delivers Umami

As the water heats up, the kelp releases flavor. While waiting for this process to occur, I marvel at the fact that a Japanese chemist named Kikunae Ikeda, in 1908, discovered that kelp releases the delicious compound known as glutamate, which produces the savory taste the Japanese have long referred to as umami. Ikeda realized the compound could be manufactured into a white powder which we know and love today as MSG—or, according to those who write the ingredients list on chips and other tasty snacks at your grocery story, "hydrolyzed vegetable protein." Take a break from Doritos, because miso soup is Mother Nature's MSG. Drink up.

The one or two remaining purist Buddhist chefs in Japan who are actually vegetarian would be content to use only the kelp broth as the soup base. However, most everyone else proceeds to a second stage in the production of the broth. In other words, if you are served real miso soup, it's almost certainly not vegetarian. You may be surprised to hear this. Many great creatures have been killed for miso soup.

Bonito: Basically Moldy Fish Scrapings

But don't worry, we're only talking about fish here, not birds or pigs. (I personally rank fish higher than chickens, but that's just my opinion.) Miso soup doesn't taste like fish soup, you are thinking. True. Here's why:

A glass measuring cup full of dried bonito flakes with a package of bonito flakes next to it.

Bonito flakes.

Fishermen catch skipjack tuna (also called bonito). Then, specially skilled chefs (probably on their way into or out of an insane asylum) simmer the fish, smoke it for ten or twenty days, then infect the fish with mold and lock them in boxes for two weeks, then scrape off the old mold and add new mold and lock them in boxes for another two weeks. They repeat this procedure several times. During this process digestive enzymes break down the muscle tissues of the fish into delicious amino acids, especially inosine monophosphate, also a source of umami flavor. After several months the fish have dried out to the consistency of 1,000-year-old trees and are then shaved with a carpenter's plane into flakes that are thinner than paper, a process you can witness at 7 a.m. outside the Tokyo fish market. These bonito flakes are called katsuo-bushi in Japanese, which translates approximately to "dried moldy fish confetti made by insane people."

I pack two cups worth of bonito flakes into a measuring cup and have it standing by, ready for the water with the kelp to nearly come to a boil.

The Art of Making Miso


I also prepare some other ingredients. Miso is necessary to make miso soup, and I finally know what it is—basically moldy rice and beans sitting around way too long (yes, mold is a surprisingly instrumental part of the miso soup production). But there is a great art to making it. An art that is mostly dead.

There is one little farm in the remote hills of western Massachusetts (near a place I once went folk-dancing) called South River Miso that makes miso the really old-fashioned way—in cypress vats with workers stomping for hours to mash the miso. Japanese apprentices go there to study the lost art. The bottom shelf of my refrigerator is full of all kinds of weird, foot-stomped, hand-made miso from here, still active with enzymes and friendly bacteria. (Don't worry, there is no toe cheese in it because the foot-stompers use protection.)

How to Make Miso Soup


I also prepare some tofu by propping it at an angle and piling heavy plates on top, just as my Japanese friends instructed. This squeezes out the water so the tofu can absorb more of the tasty miso soup. Or maybe my Japanese friends are just insane as well.


Then I cut the tofu into cubes. I also slice some leek or spring onion or something, and prepare a handful of dried wakame seaweed.


When the kelp in the pot has become all flush and thick and open and the water is steaming mightily and just about to boil, I turn off the heat and dump in the bonito flakes. I let the bonito flakes sit in the steaming water with the kelp for about five minutes, not much longer.


Then I pour the broth out through a strainer lined with cheesecloth into another pot.

Behold: this is dashi! The essential foundation broth of most Japanese sauces. It can also be served as a light soup on its own. Apparently, some discerning traditionalists in Japan will even judge a chef first on the taste of his dashi alone.

In my experience, dashi broth keeps in the fridge quite well for a number of days, but completed miso soup does not. Therefore, I set aside the broth I won't use immediately and return to the stove only enough broth for the soup I want to use now.

I put the broth back on the heat, but very, very low. I don't dump the miso straight into the broth. Instead, try spooning a ladleful of broth into a small bowl, then whisk several clumps of miso into the broth to break up the miso and liquefy it before pouring the viscous mix back into the larger broth pot. I stir and keep adding miso this way until I like the taste of the soup.

Finishing Touches

Basically, that's it—miso soup is complete. I toss in some tofu cubes and let them absorb the soup for a while, but I am very careful not to let the soup boil. I toss in the slices of leek or spring onion (or whatever I sliced).

Before serving, I sprinkle the dried wakame seaweed into serving bowls and then pour the soup over it; the seaweed absorbs the liquid almost immediately and expands.


Voila, or as the Japanese say, dekimashita! To me this soup is vastly more delicious and interesting to eat than the miso soup I get anywhere else—the unpasteurized miso from South River makes a big difference.

(A spoon is not really necessary for miso soup. Most Japanese just raise the bowl to their lips and sip, using the chopsticks to direct tofu and seaweed into their mouths.)


Often I don't stop there—if I want an entire meal, I cook buckwheat noodles and sauté something fun and green like watercress and sprinkle on shredded nori and a little Shichimi Togarashi spice and presto, it's dinner. My favorite version includes half a fillet of smoked mackerel laid on top. If you keep extra dashi broth on hand for a few days, presto again, it's another easy bowl of soup at that point.

I would say that the right miso soup is indeed special, and magical, and that there ought to be a temple to it somewhere (if there isn't already). Heck, now that you've read this, that temple could be your own kitchen.

Mother Nature's MSG. Drink up.