SouthernTurk
Unusual recipes for curious cooks.
https://southernturk.com/recipe/koji-rubbed-aged-butter
Printed July 29, 2026
Printed July 29, 2026
Fermented & Funky
Koji-Rubbed Aged Butter
Inoculate cultured butter with koji spores and age it like cheese for a spreadable umami bomb that tastes like butter went to finishing school in a sake brewery. Impossible to buy, unforgettable to taste.
Ingredients
- 1 pound high-quality unsalted butter, softened
- 2 tablespoons koji rice (rice inoculated with Aspergillus oryzae)
- 1 teaspoon sea salt
- 1 teaspoon honey
Preparation
Koji — the mold culture used to make miso, soy sauce, and sake — breaks down proteins and starches into amino acids and sugars, creating profound umami. When applied to butter's milk solids, magic happens. This is a project for the adventurous, requiring patience and precise temperature control.
Preparation
- Ensure all equipment is scrupulously clean. Grind the koji rice into a fine powder using a spice grinder.
- In a bowl, mix the softened butter with koji powder, salt, and honey until evenly distributed.
- Form the mixture into a log using parchment paper, twisting the ends to seal.
- Place in a temperature-controlled environment at 140°F (60°C) for 8-12 hours. A dehydrator, yogurt maker, or oven with just the light on can work. The butter should not melt completely.
- After the incubation period, refrigerate for at least 24 hours to let flavors meld.
- The butter will develop a slightly funky, nutty, almost cheesy aroma. Spread on warm bread, melt over steak, or use to finish risotto.
- Store refrigerated for up to 2 weeks or freeze for up to 3 months.
Note: Koji can be purchased online from specialty suppliers or Asian markets that cater to home fermentation enthusiasts.
