Mix onion and corn starch by hand in a bowl.
Combine ground pork, Japanese leek, ginger, and * marked ingredients by hand in another bowl, and add Step ① 's mixture. Stir well.
Make mixture into round balls and place on the steaming paper (cooking sheet). When you place, leave a space in between each shumai.
Cover shumai with a skin, push shumai skins by grasping by hand. Make a little hole on the top of each shumai, put green peas and push lightly.
Steam them for 10~15 mins over high heat.