food simmered in soy sauce, sugar, mirin, etc. for short-term preservation
A home-cooking technique for keeping food for a few days without refrigeration; common with small fish, vegetables, or kombu.
If you make tōzani with small fish, it will keep for a few days.
当座 (tōza, 'for the time being') + 煮 (ni, 'simmering'), referring to a dish prepared for short-term preservation.