Add shumai mixture, excluding onion and cornflour, to the bowl. Mix well until the mixture becomes almost like a paste.
Then add onion and cornflour and mix well. Cover and leave for 1-2 hours in the fridge.
Sprinkle small amount of cornflour (not in ingredients) over the tray where the shumai will be placed as you make them.
Using your non-dominant hand, make a round hole by connecting the thumb and the index finger with the rest of fingers next each other. Place a shumai sheet onto the circle made with the thumb and the index finger.
Scoop about a tablespoon heap of meat mixture (note 2) and place it in the centre of the shumai sheet.
Using the back and tip of the spoon, press the meat down gently through the hole while holding the fingers firmly. Slide the meat with the sheet downwards until the surface of the meat levels with the circle of the fingers.
Smooth out the surface of the shumai and place a green pea in the middle, if using.
Repeat steps 4 – 7 to make 24 shumai in total or until either meat mixture or the wrapping sheets run out.
*Steaming Shumai Using a Bamboo Steamer* Make a round steaming paper liner with many holes (see the video) which will just fit inside the steamer. This is to prevent the shumai skin from sticking to the bamboo. Place a wok with a cup of water over the high heat. Place the paper liner inside the bamboo steamer, then place shumai in the steamer without touching each other. If the steamer cannot take 24 shumai at once, you will need to steam them in batches. When the water starts boiling, place the bamboo steamer onto the wok and steam for 8-10 minutes until the meat is cooked through.
Serving If you are using a bamboo steamer, you could serve shumai in the bamboo steamer. If using a steamer pot/pan, transfer the shumai onto a plate. If steamed on a plate using a pot, serve the steaming plate with the shumai on. Serve with soy sauce, vinegar, chilli oil/hot mustard.
Recipe Notes 1. I used the Japanese shumai sheets which comes in a pack of 24 sheets. The size of the sheet is 6.5cm (2½") square. You could substitute it with the Chinese shumai or wonton sheets which are usually 9cm (3½") square. If the size of the sheet is larger, you will need more meat to fill up the sheet or reduce the number of sheets to make. 2. To use up the meat perfectly, I draw 4 lines on the surface of the meat crossing in the centre so that it will make 8 pieces like pizza. Then roughly divide each piece into 3 equal portions. This will make 24 lots of meat. 3. For more details on how to steam without a steamer, please visit Sakamushi Fish (Steamed Fish in Sake). You will even find out how to take the steamed hot plate out of the pot without burning your fingers. 4. It is unlikely that the shumai skin at the bottom will stick to the plate but I thought it would be pretty to have a paper liner anyway. 5. You can freeze before or after steaming them. When freezing, place each shumai without touching each other. Once frozen, you can pack them closely. Frozen shumai can be steamed without thawing. It will take 10-12 minutes.