Sunday, March 15, 2020

Koji Stock

Back in February of 2019, I wrote (here) about using Japanese ingredients, such as culinary powders and stocks, to make pasta sauces and I shared a recipe by Danny Bowien for what has become a staple in my kitchen pantry: shiitake mushroom powder. Here’s how I use the powder to make a quick yet flavorful fresh pasta sauce serving 2:  

Sauté a diced shallot in 2 tablespoons/28 grams of butter. Add 1 tablespoon/2 grams of mushroom powder to the pan and stir the mixture together over moderate heat. Add some thinly sliced vegetables to the pan. (When in season, I like to use thin slices of fresh artichoke heart or asparagus.) Pour in ½ cup or so of water, a bit more butter and a pinch of fennel pollen and/or some chopped herbs. Bring the mixture to a simmer, taste and season with salt and pepper, cover the pan and braise the vegetables for about 4 minutes. The sauce is now ready to receive the cooked pasta. Mix the pasta and sauce together for a minute over moderate heat, add freshly grated Parmigiano Reggiano and/or Pecorino Romano cheese and cook until the pasta absorbs its sauce. The shiitake powder enhances the flavor of the other ingredients without contributing a mushroom flavor. The powder makes the sauce taste delicious and savory.

When I want to add even more flavor to this pasta sauce, I use koji stock in place of water. In The Noma Guide to Fermentation (Artisan, 2018), René Redzepi and David Zilber write that they “find koji indistinguishable from magic—the best kind of magic, in fact, because anybody can wield it.”


What is koji? Per The Noma Guide to Fermentation, “[k]oji is a term that comes from Japan, where it refers to rice or barley that have been inoculated with Aspergillus oryzae, a species of fungus—a sporulating mold, to be exact—that grows on cooked grains in warm and humid environments. (In the English-speaking world, we apply the term koji interchangeably to the inoculated grains, the fungus, and the spores.)”

I first read about dried rice koji in a 2013 article by Tara Duggan in the San Francisco Chronicle. Duggan’s piece focuses on shio-koji, an easy-to-make mixture of dried rice koji, salt and water. Shio-koji tastes salty, sweet and savory all at the same time. Use it like salt to marinate meat, make pickles, and add flavor and depth to salad dressings and sauces.

The Noma Guide to Fermentation contains a recipe for shio-koji. But, better yet, Redzepi and Zilber tell the reader how to make the actual koji grains. The book goes on to suggest innovative ways to use both fresh and dried koji grains. One application surprised me: use dried koji grains to make stock. Redzepi and Zilber write: 

“One of the best possible uses for dried koji is as a flavoring for stock. Boil 1 liter water in a pot and add 150 grams crumbled dried koji (not koji flour). Turn down the heat and let the stock simmer for 10 minutes. Strain and discard the solids. What you have is a versatile, vegetarian base liquid that can be used for a whole flight of applications.”

That’s it! In 10 minutes you can create this magical liquid that enhances and deepens the flavor of food. On its own, my homemade rice koji stock smells and tastes just slightly sweet and of mushrooms, but its own unique flavor disappears as it cooks and the koji works its magic. The authors share that, thanks to koji, at Noma they “more or less stopped making long-cooked meat stocks and producing sauces via classical reductions…By cooking koji into a lighter broth, we can achieve the same rich, complex flavors without the heaviness of all that gelatin and dairy.” 

If you want to try koji stock but don’t want to make and dry your own koji grains, finding commercially-manufactured dried rice koji isn’t nearly as difficult as one might imagine. Start your search at a well-stocked Asian market. If you live in a major metropolitan area, you might find dried rice koji at a nearby grocery store with a good international food section. The brand I see most often here in the Pacific Northwest is Cold Mountain. If you cannot find dried koji grains locally, you can buy a container on-line from US and Japanese sellers.

Being me, I wanted to make my own koji grains. I used my Brød & Taylor Bread Proofer and a homemade cedar tray to hold the grains. I bought koji spores (aka koji tane) from GEM Cultures, a business here in Washington State and from Kawashima, an on-line source in Japan. Koji tane doesn’t cost too much and has a self-life of months if properly stored. By carefully following Redzepi and Zilber’s clear instructions, I went from uncooked white rice to koji grains in 2 days of mostly unsupervised attention. Making barley koji is just as easy as creating rice koji.

Is koji stock made from homemade rice koji better than stock made from Cold Mountain dried rice koji? In my experience, the homemade stock has a much deeper aroma and taste. But both produce remarkable stock.

If you haven’t checked out Redzepi and Zilber’s book, I recommend you give it a look. The Noma Guide to Fermentation explores a broad assortment of fermented foods ranging from simple lacto-ferments, such as pickled white asparagus, to mind-blowing black vegetables and garums made from roasted chicken wings. Redzepi and Zilber also explain how to use koji to make miso and shoyu.