Rice koji fermented with salt and water into a loose, salty-sweet porridge. Used in place of salt, it seasons, tenderises and helps meat and fish brown.
Japanese grocers, in tubs or as a strained liquid. Or make it: rice koji, about a third of its weight in salt, and enough water to cover, left at room temperature for a week or so and stirred daily, until it smells sweet and a little sour.
A little history
An old Japanese preparation that had a big revival in Japan around 2010, and travelled from there.
Worth knowing
As a marinade, use roughly 10% of the meat or fish's weight, for a few hours to overnight. Wipe most of it off before searing or grilling — it burns before the inside is done.