Miso is a Japanese seasoning paste made by fermenting cooked soybeans, sometimes with added rice or barley, using a mould starter called koji. The koji mould breaks the soy protein down into amino acids over a long fermentation, while salt keeps unwanted spoilage bacteria in check. Fermented cabbage is called sauerkraut instead, and fermented black gram goes into products like idli and dosa, so those don't fit. The correct base ingredient for miso is soybean.