This fermented soybean paste is as staple of Japanese cuisine. Miso is made by steaming and crushing soybeans, then adding sea salt and koji, a culture made from grains like rice and barley that triggers fermentation.
Variables like the type of koji, the ratio of soybeans to koji, salt content, and length of fermentation lead to innumerable varieties of miso ranging in color from pale golden yellow to rich chocolate brown. Generally, the lighter the miso, the sweeter and more delicate its flavor.
Look for miso in plastic tubs or bags in the refrigerated section of Asian markets or health-food stores.
Always add miso toward the end of cooking and never boil it, as high heat will destroy both its flavor and nutrients. For the smoothest sauces and soups, whisk miso into an equal amount of slightly warm broth until smooth, and then gradually stir the thinned miso back into the pot.
Miso keeps for up to a year if sealed well and refrigerated.