Shio Koji Butter

Why This Recipe Works

Koji is an ancient mold that’s used to produce soy sauce, miso, fermented bean paste, and sake. Shio koji is another traditional use of this mold. It’s made by combining rice koji (cooked rice that has been inoculated with koji spores and then dried), salt, and water and letting the mixture ferment for about a week, during which it develops a sweet, fruity, slightly funky aroma. Shio koji, which can be made at home or purchased, is often used as a marinade because it is rich in protease enzymes (which break down proteins), so it can create an array of new flavors in protein-rich foods. We also like to stir a small amount of shio koji into softened butter (along with a little salt and minced herbs) to create a lightly sweet, savory compound butter for steak or vegetables.