I have cooked dried beans in the past — lots and lots of dried beans — but have never taken as much care as I now do when I prepare kuromame, the elegant sweetened black beans eaten during o-shogatsu, the New Year celebration. The first year I was allowed to watch (for the first several years young cooks only get to watch), I was immediately impressed with the time and effort put into the process of handling each individual bean.
Dry, black soybeans are first selected for their size, shape and color. Large, perfectly oval dark beans are preferred for purely aesthetic reasons. Then, the beans are sorted through, with a small handful at a time placed on a white sheet of paper so that stones and other foreign matter may be easily seen and disposed of before cooking. Next, the beans are washed gently so that the skin is not bruised, causing the bean to burst when cooked. Covered in a good amount of water, the beans are let to stand overnight. This is the one part of the process in which a watchful eye is not necessary.
The next day, the soaked beans are set to the flame for the first time. The soaking water is used, but many chefs insist that the tannins released in the soaking process help to soften the beans. In this water the beans are brought quickly to a boil, causing foam and scum to rise to the top. The scum is removed and then discarded. While it contains properties that soften the beans, this soaking water also contains a lot of the compounds that make beans "the musical fruit." Discarding it and starting with fresh water will make a difference to the stomachs of those who will later consume the kuromame.