Deeply savory, salty, and sweet, miso is one of our all-time favorite ingredients to cook with for the complex, earthy flavor it lends to anything it touches. It's an umami-rich fermented soybean paste that's a staple in Japanese cuisine, but that's only scratching the surface. Traditionally, miso is made by mashing together either steamed rice or barley with cooked soybeans, salt, water, and koji — rice that's inoculated with a specific type of fungus that kickstarts the fermentation process. This mixture then ferments under controlled conditions for anywhere from a few days to three years, depending on the variety.
Miso can also be made with buckwheat, millet, rye, chickpeas (an excellent option for those with soy allergies), walnuts, corn, quinoa, azuki bean, or some combination of these ingredients with rice, barley, or soybeans. The common thread is koji, which is also a key ingredient in sake production.
When cooking with miso, keep in mind that it's a living food, so, it's best to use it in raw dishes or add it toward the end of the cooking process, as excess heat kills off the beneficial microorganisms and can also mellow out its flavor. Though it's a living food, miso has an impressive shelf life, thanks to its high salt content. Once opened, most varieties can last for a year (or more!) if stored refrigerated in an airtight container.