Yam must be stewed in casserole. The wok will turn black and the stew will feel sticky. You can stew pig's hands with yam.

Both yam and lotus root can be put in when the ribs are cooked on a big fire, and then cooked on a small fire, but the wax gourd can't rot easily. Wait until the ribs are almost cooked, or they will all melt into the soup. It is best not to put red dates and medlar in summer. If it is stewed in winter, you can put some spices and other things before turning on the small fire, and then you can put them in.