The alchemist is in: Jeremy Umansky’s new cookbook lets the rest of us in on the magic of koji

Cue the “fun guy” jokes: From fermenting to foraging, Jeremy Umansky is a self-professed fungus fanatic—and it’s earned him global renown.
Here in Cleveland, Umansky is best known as the James Beard-nominated co-owner of Ohio City-based Larder Delicatessen and Bakery. Yet he is also one of the country’s foremost experts on koji—the fungal microbe responsible for the creation of soy sauce, miso, sake, and more. Though it’s been used in East Asia for thousands of years, koji has long been a relative unknown throughout the rest of the world.
“It’s literally probably the most important ingredient in a dozen different Asian cuisines,” Umansky says, “yet nobody outside of Asia really knows it or understands it.”
That’s about to change, thanks to Umansky’s latest endeavor. In collaboration with his friend Rich Shih, an engineer and home cook, Umansky has co-authored Koji Alchemy: Rediscovering the Magic of Mold-Based Fermentation (Chelsea Green Publishing). Set for release on May 6, it is the first English-language book dedicated to demystifying the processes and concepts of age-old koji-based fermentation; it also introduces new and modernized techniques.

(photo: Andrew Wang)

So what exactly is koji? Umansky explains that the word refers to both the mold spore itself, scientifically known as Aspergillus oryzae (“It’s the equivalent of our sperm and egg, or a plant’s seed”) along with the process of using it to ferment food (“It’s what transforms the edamame bean into soy sauce”).
When koji-the-spore is applied to various foods, koji-the-process begins—breaking apart carbohydrates, proteins, and fats on a molecular level and literally changing the taste of the foods as we know them.
“Essentially what koji does, at its simplest, is make anything it comes into contact with more delicious,” Umansky says. “It makes it taste better.”
The tiny microbe is thought to have been used in food preparation since as early as 7000 BCE. It’s a key element in Asian staples such as amino pastes (think Korean gochujang and Japanese miso), amino sauces (like shoyu, or soy sauce), alcohol (including sake), and kome-koji (literally“koji rice”)
More recently, though, contemporary chefs like Umansky and Shih have begun using koji on everything from meats and cheeses to beans and barley—and even on popcorn and chocolate.
“This is a very unknown area to a lot of people outside of Japan,” Umansky says, “so as Rich and I started to work with it more, we became known as people at the forefront of it outside of Asia—putting Western sensibilities on it through our specific lenses of cuisine.”
For Umansky, that means endless food combinations and flavor profiles. Larder’s vegetable charcuterie board, for example, includes beets and carrots that are smoked, spiced, and inoculated with koji; meanwhile, koji-inoculated black beans are used in everything from coleslaw to salad to gravy. Speaking of gravy, that’s slathered atop thick slices of koji-cultured hen-of-the-wood mushrooms, served up on breakfast biscuits. There’s also beef blood sausage made with black koji and green tomatoes pressed in koji vinegar… the list goes on and on.
Umansky is thrilled to share his knowledge with new audiences, and Koji Alchemy is designed to do just that. Packed with techniques for growing and curing koji, it also includes more than 35 recipes for many of the dishes he makes at Larder—where some of the Western world’s most forward-thinking koji experimentation is taking place.
“The research and study and practical application of this all happening in Cleveland—and virtually nowhere else,” Umansky says with pride. “Outside of Japan, Cleveland has become known as the home of koji.”
-Kate Kaput