on size

Onsize (or "on size") is a traditional Japanese condiment made from fermented soybeans, koji (aspergillus oryzae mold), salt, and sometimes grains, resulting in a thick paste with a deep umami flavor profile. The ingredient undergoes a lengthy fermentation process—typically six months to several years—during which enzymatic breakdown develops complex aromatic compounds and amino acids. The paste ranges in color from light tan to dark brown depending on fermentation duration and specific ingredients used. It has a savory, slightly sweet taste with pronounced saltiness and a thick, spreadable consistency.

Onsize is primarily used as a base flavoring agent and condiment in Japanese and Asian cuisines, where it adds depth and umami richness to broths, marinades, dipping sauces, and stews. It is commonly dissolved into soups, particularly miso soup (misoshiru), or mixed into dressings and glazes for vegetables, tofu, and grilled proteins. The paste can also be used as a table condiment for seasoning individual dishes. Its concentrated flavor means small quantities are typically sufficient, and it pairs well with dashi broth, rice vinegar, and mirin in traditional applications.