Aspergillus oryzae spores, commonly referred to as koji mold. The powdery spores are sprinkled on warm rice and allowed to ferment for 24 to 48 hours. During this time, flavor blooms as the rice transforms into koji – the backbone of miso, soy sauce and sake.
Shio-koji, or salt koji, has become a workhorse ingredient in the kitchen at Bar Tartine in San Francisco. It is possible to purchase the slurry in Japanese markets, but Chefs Cortney Burns and Nick Balla make their own by mixing koji, salt and water and allowing it to ferment in a humidity and temperature controlled environment. They use it to marinate meats and fish and mix it 1 to 2 with cultured butter for an umami rich spread. It can also be used to correct the balance in soups and braises. Burns is most excited about a dish at the restaurant right now that features Chad Robertson’s koji sourdough bread spread with koji butter and topped with a koji-potato puree, beef tartare and a sprinkling of bottarga.
Hear Burns talk about how she and Balla use koji at Bar Tartine in her interview with Good Food’s Evan Kleiman. Keep reading for Bar Tartine’s Koji-Marinated Roast Chicken recipe below.