Otoshibuta is a Japanese “drop lid.” Instead of sitting on top of the pot itself, this wooden lid fits cleanly inside the pot, resting on the boiling liquid. These have been used in Japan for hundreds of years for nimono, or simmered foods.
If you aren’t familiar with the concept of a drop lid, you probably have the question: why not just use a normal lid? Well, there are a few advantages to otoshibuta.
To start, they ensure that the boiling of the water or other liquid doesn’t create too large of bubbles that pop violently on the surface. This prevents the simmering liquid from jostling around more delicate ingredients that could be torn apart, helping maintain the physical integrity and texture of the dish. Also, the otoshibuta prevents greater evaporation, with the end result being more concentrated, flavorful food.
Because they’re typically made of wood, otoshibuta must be taken care of properly. The first part of this is thoroughly washing and hand-drying after each use. Beyond that, you must soak it in water briefly before use to make sure the porousness of the fiber doesn’t absorb the flavor of the liquid, broth, or water being simmered. Otherwise you risk “seasoning” the otoshibuta and passing on the flavor of a previous dish when you use it next.