Nab, or hot pot as its often called in english, is a winter staple in most japanese homes, and the epitome of japanese comfort food. Its basically japans version of the casserole. You can put almost anything into it and it feeds a lot. A typical nab is made in a pot called donabe made of clay which helps retain heat and keep the soup warm for longer, but any pot will do. I use an aluminum pot which cooks faster.