Miso paste is a staple Japanese cooking ingredient made by fermenting soy beans, and occasionally other ingredients such as barley or rice, with koji (an edible mould that is cultivated on rice and other starches). Miso can vary in flavour and texture from sweet and smooth to savoury and course, depending on the ingredients used and fermentation time. If you are looking to explore the wide world of miso, Japan Centre's Miso section is a good place to start.