Uchimame are soybeans that have been steamed and then flattened, one at a time, with a wooden mallet, so that each of them opens out into something like the shape of a flower, and then dried and stored.

Being crushed, they cook fast. They also take up flavor quickly, which is the entire reason they exist. A household with work to get to could put a soup together without waiting for beans to soften.

The dish belongs to Kohoku, the country north of Lake Biwa, where the snow is heavy and soybeans were the reliable protein through winter.

The soup is simply miso soup with these beans in it, and in that district, through the cold months, it is not treated as one option among several. It is also served at the hoonko observances at the temples, the memorial services for Shinran, often enough that it has a second name: okojiru, the temple-service soup. The leek that goes in is sometimes shinaga-negi, grown at Azuchi in Omihachiman and named after Oda Nobunaga for being thick and unrestrained. Kohoku grows a great deal of soy itself, so both halves of the dish come from the same fields. The work with the mallet is done in advance because mornings are short.