Always eager to try new fermented foods, I recently bought a $4 tub of koji at an Asian supermarket. Koji is a fermented rice product from Japan, not super-popular, but common enough in some Japanese dishes because of its intense umami flavor.
Hoping to bring a different zing to some grilled ribeye, I originally considered it as part of a marinade, but then I happened upon an article in Bon Apetit that suggests it as a short-cut for dry-aging beef.
So I tried it and it works! Leave it soaked with koji uncovered in the refrigerator for about two days. Remove the rub (it’ll burn otherwise) and grill. The result is a pleasing, somewhat umami flavor, more tender than typical ribeye. Highly recommended.