Make Your Own Fava Bean or Soybean Miso Paste (Ultimate Guide)

 

Miso is a traditional Japanese seasoning made by fermenting soybeans with salt and koji (which itself is made by inoculating rice with Aspergillus oryzae, a type of safe fungus). It’s a thick paste used in a variety of dishes to impart a rich umami flavor, often described as savory and slightly sweet. Miso has become so popular in part because it’s incredibly versatile—perfect for soups, marinades, dressings, and glazes. It’s also packed with nutrients like protein, vitamins, and probiotics, which can support gut health and overall well-being. Plus, its deep, complex flavors transform ordinary dishes into extraordinary culinary experiences. What’s not to love?

This recipe has got you covered!

Countless recipes abound for soybean-based miso, which is the most popular option, but broadbean (fava bean) miso is another great choice. This recipe can be used to make either type of miso with just a couple of minor adjustments noted below! This recipe also gives guidance for cooking the beans either through the conventional stovetop method or an “Instant Pot” type device or pressure cooker (which yield terrific results).

The fact is any bean or even any legume could be used to make miso paste, and you’re encouraged to explore as you gain experience. Lentils, chickpeas, black beans, even peas (hello Pea-so Paste!) will make unique and delicious misos. However, soybean and broadbean are classics; they’re sure to deliver a great product and are a good starting place.

This is also designated an easy recipe because it was written with pre-cultured dried rice koji in mind (which is used to ferment your beans), i.e., this kind of koji you can simply buy. (You can make rice koji at home too, but the process is rather involved and isn’t covered here.) Unlike homemade rice koji, the purchased kind will need to be moistened a bit with your bean water, explained below. Fava bean miso produces an even more intense umami flavor and yields the best results as a longer-term ferment, which means a higher salt content is suggested to carry it through an extensive ferment of possibly years. This salty aspect of fava miso is also notable, so if you prefer a lighter miso paste that is a little less salty and can be ready in as few as six months, soybeans are suggested.

Yield:

  • About 3 quart jars (3.5 kg)

Shelf Life:

  • Shelf life in fridge is around one year (or more) after the desired ferment time is complete provided the final jar is kept in cold storage. It may instead be kept unopened at room temperature. Note that in this scenario, after a couple years, the umami will actually start to deteriorate (it may still be a desirable product). Once the ferment time is complete and the jar opened, the weights and tamari should be removed and the miso transferred to a smaller jar (to reduce air space up top) to reside in cold storage.

Equipment:

  • 3 half-gallon jars, or a single storage device of equivalent size (1.5 gallons or 5.75 liters)
  • Large saucepan (or instant pot)
  • Colander
  • Potato masher (or food processor or meat grinder)
  • 1-2 large mixing bowls
  • Sanitizer (e.g., OneStep) or vodka/grain alcohol as an alternative
  • Kitchen gloves
  • Muslin cloth cut to the shape of the vessel, for covering the paste (some use cling wrap, but it may be unwieldy)
  • Weight(s) roughly equivalent to the weight of the miso paste (to apply on top during fermentation)

Ingredients:

  • 1 kg dry fava beans (broadbeans) or soybeans, organic suggested
  • 1 kg koji rice
  • For longer-term ferments of 1+ years: 400g salt (20% weight of the dry products); reserve 2-3 TBSP of the salt for later
  • For shorter ferments of 6-9 months: 250-300g salt (12.5-15% weight of the dry products); reserve 2-3 TBSP of the salt for later
  • Retained 3 TBSP bean liquid (use sparingly, to moisten the rice koji as needed)

Directions:

  1. Triple rinse the beans then cover with water and soak overnight (or 2-3 nights covered, refrigerated).
  2. Cook the beans:Fava Beans:
    • Saucepan: Drain the beans after soaking, transfer to a saucepan and add water to cover. Bring to a boil on high heat, removing any foam that forms. Reduce heat, cover, and simmer for about 45 minutes until they are soft enough to crumble when pressed. Instant Pot: Add the beans and 7 cups of water. Pressure cook for 15 minutes, followed by a natural venting process.
    Soybeans:
    • Saucepan: Drain the beans after soaking, transfer to a saucepan and add water to cover. Bring to a boil on high heat, removing any foam that forms. Reduce heat, cover, and simmer for about 2 hours until they are soft enough to crumble when pressed. Instant Pot: Add the beans and 7 cups of water. Pressure cook for 25 minutes, followed by a natural venting process.
    Notes for either method: Beans should easily crumble when pressed. Reserve some of the bean water for later. Beans will still have their membranes, which may be kept on during fermentation. These break down easily for soybeans, but fava bean membranes are thicker. Some choose to remove them before fermentation, but it can be cumbersome or require a suitable food mill. Processing fava beans in a food processor or blender before mixing with the rice koji is advised. However, with a long enough ferment, the membranes will largely break down on their own, and additional blending or mashing isn’t absolutely required.
  3. Strain the beans in a colander, reserving about ¼ cup of the bean liquid, and mash or process the beans until it forms a smooth paste. Allow them to cool to room temperature.

4. Prepare the koji-salt mixture: In a mixing bowl, combine the salt and rice koji. With very clean or gloved hands, break up the rice koji and work the salt into it until uniform. Add 1 to 2 TBSP of the bean water and evenly mix by hand, so that the mix holds together when squeezed. Start with 1 TBSP bean water and only add more if, after 30 minutes of allowing the water to penetrate, there still isn’t enough moisture. Use a maximum of 3 TBSP bean water. (Do not use bean water unless it is still fresh; alternately, you may use up to 3 TBSP clean water; also note that excessive addition of moisture can make miso more prone to molding or souring.)

5. Combine the bean paste with the koji-salt mixture: Add the bean paste to the koji-salt mixture. Work the two together vigorously until a uniform paste is achieved (the potato masher or processor may be used for this step as well).

6. Sanitize the fermentation vessel: Before the final step of adding the paste to the fermentation vessel, the vessel should be sanitized (with a product like OneStep) and/or carefully wiped down with vodka or grain alcohol using a clean cloth, then completely dried. Wear clean kitchen gloves while cleaning the vessel. This ensures that no unwanted bacteria or mold interferes with the fermentation process.

7. Form the paste balls: Form balls of the paste while squeezing it vigorously by hand. You want to eliminate any air pockets inside the paste. Each ball should be about the size of a baseball (or smaller) and can be placed in the fermenting vessel. As balls are added, they must be firmly pressed down so that any air pockets between balls are completely eliminated. The jar(s) should be filled about halfway with the paste, and there should be no visible signs of air or cracks in the bean paste. Fermentation vessels that aren’t glass or transparent won’t allow you to visibly check this on the sides, so glass is a good choice for beginner miso makers to see what is happening.

8. Salt the surface: The reserved 2-3 TBSP of salt should now be sprinkled evenly atop the surface of the ferment to help protect against mold and fungal growth. It is common to see some fungal surface growths when opening miso for the first time after several months, and these can simply be removed; they are not harmful and the miso batch should not be regarded as ruined. Note that the dark liquid that forms at the top is tamari and may be used. To collect tamari, simply pour off the liquid that accumulates at the top and store it in a clean container. It can be used as a soy sauce substitute or as a seasoning in various dishes.

9. Cover with muslin cloth and add weights: The muslin cloth should be cut or shaped to cover the entire surface of the ferment. Then a heavy weight, ideally about equal to that of the paste, should be added. Good options for weights are clean zip-top bags of salt, sealed bags of stones or marbles, fermentation weights, or other suitable sanitary items. As the paste ideally will fill about half the jar or container, once the weight is added, there will be little headspace remaining at the top of the vessel.

10. Seal the vessel: Apply the vessel lid or cover tightly. You can also use a few layers of packaging tape around the lid and top of the jar to completely seal off any potential avenue for oxygen or microbes to enter. A popular alternative is to completely wrap the vessel in heavy paper and tape or tie it shut. The vessel should then be placed in a cool, dark environment (ideally between 55°F and 75°F) for the desired length of time. Maintaining a stable temperature and avoiding exposure to direct sunlight will help ensure a successful fermentation. It is also a good idea to label the jars with the date they started fermenting to keep track of the fermentation time. It is okay or even desirable for the miso to change temperature with the seasons, but extremes in heat or cold should be avoided.

11. Storing the miso: Once the miso is open, the weights and tamari should be removed and the miso transferred to a smaller jar to reside in cold storage. Since I tend to divide this recipe into three half-gallon jars, with each jar filled about halfway, the actual amount of miso from each jar fits perfectly into a quart jar. It may be stored in the refrigerator, which will help slow further fermentation and maintain its current flavor, but can also be kept in a cool, dark location. Stored in the fridge, expect the miso to stay just as robust and usable for about a year. Individual miso pastes can somewhat vary.

Left is a completed miso. On the right is one just started. Note the normal difference in color, due to some chemical reactions over time.

Uses for Miso Paste

Here are some of the most popular uses for your homemade miso! More and more recipes are being added here as well. Check out my miso banana bread and cookie recipes and see just how versatile miso paste is!

Miso Soup: A classic choice! Just dissolve a spoonful of miso paste in hot dashi broth, add tofu, seaweed, and green onions for a comforting and delicious soup.

Miso Glaze: Use miso paste to create a savory glaze for fish, chicken, or vegetables. Mix miso with a bit of mirin, soy sauce, and sugar, then brush it over your food towards the end of grilling.

Miso Dressing: Whisk miso paste with rice vinegar, sesame oil, soy sauce, and a touch of honey for a flavorful salad dressing. It’s perfect for drizzling over greens or using as a dipping sauce for vegetables.

Miso Marinade: Create a marinade for meats or tofu by combining miso paste with ginger, garlic, soy sauce, and a bit of sake. Let your protein of choice soak up the flavors before cooking.

Miso Butter: Blend miso paste with softened butter to create a unique and delicious compound butter. Spread it on bread, melt it over steamed vegetables, or use it to enhance the flavor of pasta dishes.

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