This seemingly simple wooden piece, called a 'drop lid' in the United States, is known as an ‘otoshibuta’ in Japan. Its diameter is meant to be smaller than the diameter of the saucepan so it can fall into the pot and lay directly on the ingredients being cooked. This serves to trap flavors into the broth and ingredients as they simmer in the pot. The lid works by circulating and increasing heat underneath it while the broth bubbles up, cooking the ingredients quicker and more evenly. The higher temperature also works to concentrate flavours by evaporating liquid and caramelizing sugars in the broth. It also provides a barrier that will stabilize ingredients so they don’t break apart and require less stirring. The drop lid is key for this traditional Japanese way of simmering called “nimono”. Designed by Koizumi Studio, and available from Nalata Nalata in New York.   Square Meal