Sundae ice cream is soft ice cream, there is no hardening process, and the expansion rate is 30% to 60%. Pour the cornstarch into half a cup of cold milk and mix thoroughly. Add sugar and heat together. Add the cornstarch and stir constantly. Cook for 10 seconds until the milk thickens and then remove from the heat. After cooling, mix in the sherbet and fresh cream, put it in the refrigerator, and serve after it solidifies.