To truly enjoy wontons, you should fill them yourself. A good filling combines contrasting flavors and textures. In this recipe the soy sauce, rice wine, and sesame oil flavor the pork, and the sweetness of the water chestnuts, the smoky mushrooms, the sharp scallions and ginger, and the salty ham provide contrast. The filled wontons are blanched briefly to rid them of their cornstarch coating so that they won’t cloud the soup. Once blanched, the wontons can be kept refrigerated for a day or two until they are used.