I lived for a while in Yokohama when I was in my early teens. Yokohama, Japan is a major harbor in Tokyo area and is known for many Chinese restaurants and various immigrants, especially Chinese. So, it is no wonder shumai became very popular in Yokohama and Yokohama style shumai became famous thoughout Japan. I've had my share of shumai since leaving Yokohama and I am generally not happy with most of the offerings outside of Japan. The problem is the texture. Most shumai filling is too hard - like biting into small hamburger - you can literally bounce filling off the wall hard after steamed. You can use round gyoza wrappers, pot sticker wrappers or square wonton wrappers. I prefer gyoza wrappers because Japanese style wrappers are generally thinner, but if you cannot find it, please use either pot sticker or wonton wrappers. You will need about 35- 40 wrappers. There may be leftover - more below. If you do not have bay or sea scallops, use all shrimp along with ground pork. I like the taste and texture when it has some bay or sea scallops though. What I do with the leftover filling is form into small hamburgers and saute with a bit of oil. For each wrapper , use about 2 tsp filling. Please see various photos of before and after.