From the rich broth to the velvety cubes of winter melon a gourd commonly used in Chinese cuisine for the wonderfully soft texture it takes on during cooking this wholesome soup is immensely satisfying. Although the winter melon's delicate white flesh has no distinct taste of its own, it absorbs the broth's flavor. We recommend buying a good-quality organic free-range chicken to get the best results. Since Chinese ham is unavailable in the United States, we substitute Smithfield ham. But other cured hams, such as prosciutto, also work well.