When making mutton rolls at home, wash or soak the prepared mutton with clear water first, usually for about half an hour. The purpose of soaking mutton in water is to remove blood stains from mutton. Sometimes the mutton slices we buy are black, that is, the blood is not cleaned. In addition, the mutton is soaked in water and then rolled, so that there will be no large amount of floating powder when the frozen mutton slices are rinsed in the soup pot. Therefore, the mutton must be soaked in water when it is rolled.