Miso soup is a staple in Japanese cuisine, known for its comforting umami flavor and health benefits. I enjoy it throughout the year.

You can find some great miso soup bases available in major supermarkets and Asian specialty markets—I prefer the versions that come as a thick liquid or paste base, as opposed to the powdered stuff.

Although the soup is quickly made using store-bought miso base, making your own miso gives you a chance to conduct a miniature science experiment in your home kitchen. The only downside in my mind is the amount if time required to make this, as it can take at least six months from start to finish.

This recipe will guide you through the process of making your own miso paste at home, and then will explain how to use the paste to create a comforting miso soup.

Homemade Miso Soup

Miso soup is a staple in Japanese cuisine, known for its comforting umami flavor and health benefits. I enjoy it throughout the year.
You can find some great miso soup bases available in major supermarkets and Asian specialty markets—I prefer the versions that come as a thick liquid or paste base, as opposed to the powdered stuff.
Although the soup is quickly made using store-bought miso base, making your own miso gives you a chance to conduct a miniature science experiment in your home kitchen. The only downside in my mind is the amount if time required to make this, as it can take at least six months from start to finish.
This recipe will guide you through the process of making your own miso paste at home, and then will explain how to use the paste to create a comforting miso soup.

Ingredients

For the Miso Paste:

  • 2 cups dried soybeans
  • 1 cup Kosher salt
  • 1 cup Koji (rice fermented with Koji spores), available at Asian grocery stores
  • ¾ cup warm water, or more as needed

For the Miso Soup:

  • 4 cups water
  • ½ cup homemade miso paste
  • ¼ cup wakame (dried seaweed), rehydrated in water
  • ½ cup extra-firm tofu, cut into small ¼” cubes
  • 2 scallions, finely sliced

Instructions 

For the Miso Paste:

  • Soak the dried soybeans in 6 cups of water overnight.
  • The following day, drain the soybeans from the liquid they soaked in.
  • Place the drained soybeans in a heavy-bottomed pot, and cover with fresh water by 2 inches.
  • Cook the soybeans on medium heat until they are soft and can be easily mashed, roughly 3 hours.
  • Once the soybeans are fully cooked and tender, drain them again and let them cool.
  • Once the beans have cooled, mash the beans to a paste consistency, or process using a food processor or immersion blender.
  • In a food processor bowl, combine the koji, warm water, and salt together.
  • Process the mixture in a food processor until it reaches a paste-like consistency.
  • In a large bowl, mix the blended soybeans and the koji and salt mixture together.
  • *The paste should form a stiff mixture that can hold its shape when squeezed into the shape of a ball. If you find your mixture is too dry and crumbly, add a bit more water.
  • Clean and sanitize a mason jar.
  • *If you don’t have sanitizer solution, just make sure your mason jar is incredibly clean, washed with really hot soapy water and rinsed thoroughly.
  • Pack the miso mixture tightly into a clean glass jar, pressing down as you go along to ensure there are no air pockets.
  • Leave about 1 inch of space at the top of the jar.
  • Cover the whole surface of the miso with a very thin layer of salt.
  • Cover the salt surface with a layer of plastic wrap, ensuring that the plastic wrap is pressed down firmly against the paste.
  • Weigh the layer of plastic wrap down.
  • *To weigh down the plastic, I like to take a Ziplock plastic bag and fill it with something like white granulated sugar or salt, and place that plastic bag on top of the miso paste to weigh it down evenly.
  • Cover the jar with a piece of clean cloth, and secure with a rubber band and loosely-fitting lid.
  • Store the jar in a cool, dark place for at least six months to allow the miso to ferment.

For the Miso Soup:

  • To prepare the miso soup, start by bringing 4 cups of water to a boil in a soup pot.
  • Place the homemade miso paste in a small bowl, add in a half cup of the hot water, and whisk until smooth.
  • *This will ensure the miso dissolves more readily into the soup.
  • Rehydrate the wakame with some of the hot water and cut your tofu into cubes.
  • Add the rehydrated wakame and tofu cubes back into the simmering water.
  • Let the contents cook for a few minutes, until the wakame is fully rehydrated and the tofu is heated through.
  • Reduce the heat to low, and then slowly whisk in the miso paste.
  • Pour the soup into bowls, and garnish with the sliced green onions.
  • Serve hot.

Notes

The miso paste will keep for a long time.
If you want to go deeper into the world of koji, there are several distinct types of products that rely on different types of koji in their fermentation and production.