Photo by Kenji Miura
Author Notes

Do not be intimidated by the length of this method. The explanation is longer than the process! Once you have made miso, you will know how truly simple it is and that the result is exponentially more tasty than what you can find on the shelf. And it will be yours. —Nancy Singleton Hachisu

  • Makes 7 1/2 pounds, or enough miso to last until your next batch is ready
  • 2 pounds (1 kilogram) best-quality, non-GMO dried soybeans
  • 2 teaspoons best-quality organic miso (or previous year’s homemade miso) to use as seed miso for the new batch
  • 2 pounds (1 kilogram) brown or white rice koji
  • 14 ounces (400 grams) fine white sea salt
In This Recipe
  1. Start the process about two to three months before the weather starts to warm, when it's about 50° F out (the miso will need to ferment outside over the warmer months.) In a large pot of cold filtered water, soak the soybeans for 18 hours. Drain the beans, return them to the pot, then refill the pot with water to about 5 inches (10 centimeters) above the beans. Bring to a boil over high heat, lower to a simmer, and cook for about 1 1/2 to 2 hours, uncovered, until the beans are soft. The idea here is to simmer the beans in just enough liquid so that they cook through, but that most of the liquid will be boiled off eventually. (Traditionally, the beans are steamed for 1 1/2 hours in wooden steaming boxes stacked over a large cauldron set over a very hot wood fire. N.B.: If you steam the beans you will need to double the amount of seed miso and water that you add to the mash with the koji and salt.) The beans can also be cooked in batches in a pressure cooker for about 20 minutes over high heat.)
  2. While the beans are cooking, slowly whisk 1/2 cup of hot water into the seed miso, then allow to cool to room temperature (the solution should be like a very thin miso soup in consistency).
  3. Drain the cooked beans and start mashing them into a coarse consistency. I like to grind them roughly in batches in the Japanese grinding bowl (a suribachi). Alternatively, you can run the cooked soybeans through a sterilized meat grinder. Or, you can opt for the low-tech squeeze between your thumb and index finger method. When the beans are smashed to your satisfaction (chunky or smooth), allow them to cool to room temperature (too hot and it will kill the spores). Pour in the rice koji, then sprinkle in about 80% of the salt, and add in the miso thinned with water. Knead well to distribute the rice koji and salt with the mashed beans.
  4. Place a large crockery pot, small wooden barrel, or food-grade plastic vat on the floor, with a piece of plastic sheeting underneath. Then, using your hands, form tennis ball—sized spheres of bean mash and throw them into the container with all of your might. Whack! Splot! You are looking for a satisfying splat that sounds like thunk rather than a weak glurp. Or (if you are lazy like me, with stunningly bad aim), you might mash the balls in with your fist and the heel of your hand to ensure that all air pockets have been filled. The bean mash should only fill the container about halfway full. Pat down the surface of the mash with the flat of your palm and sprinkle with the remaining salt. At this point, you can store the unfermented miso mash in the refrigerator until the weather cools to at least 50° F. (The miso needs to go through a cold winter, a cool spring, and a hot summer to properly ferment.)
  5. Smooth a clean muslin cloth across the surface of the mash and let it drape down over the sides of the container to keep out flying leaves or other debris. Place a wooden or plastic drop lid on top of the cloth-covered mash surface and weight it evenly with 4 1/2 pounds (2 kilograms) rocks or heavy objects that equal at least the weight of the mash. Cover with one more large muslin cloth and wind some twine a couple of times around the circumference of the barrel to tie the cloth in place. The cloth will act as a mold barrier and will become scarily dusted with green mold spores, so don’t skip or replace with plastic. Carefully remove to wash when you stir the miso.
  6. Let the young miso sit undisturbed in a shaded area outside until the weather warms. From May, start stirring the miso about once a month to avoid mold as the fermentation arc starts to ramp up. During the hottest period, you should probably stir the miso (from the bottom up) every 2 weeks to avoid mold forming. Ideally the weather should become muggy, and the temperatures should rise to about 100 °F (38° C) at the height of the summer, but avoid direct sunlight. If you see any mold on the surface, carefully scrape it off. Clean the inside surface walls of the container with a vodka- or shochu-soaked cloth to deter mold. If you are feeling particularly adventurous, you could smooth a 1-inch (2.5-centimeter) layer of sake lees across the surface of the miso in June or July to seal and inhibit mold produced by oxidization. In this case, you really want to completely cover the surface to make a homogeneous layer (you still need to use the cloth, drop lid, weights, and outside cloth cover). Peel off the sake lees when the weather turns cool in the late fall, and recycle the lees as an instant pickling bed.
  7. If you have not sealed the miso with sake lees, check the miso after the summer to see if it has mellowed to your liking. At this point, you can refrigerate it or just leave the miso in its fermenting container until you start your next batch in the coming winter. No need for weights once the miso is done—you can leave it outside if the weather is cool; otherwise store it in the fridge for easy access.

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Nancy is the author of Preserving the Japanese Way and Japanese Farm Food.