Thaw green peas by leaving it in water and mince the onions. Sprinkle potato starch over the onions and mix well (This is to draw out moisture from the onions and prevent the filling from becoming watery).
In a large bowl, add ground pork and season with salt, pepper, oyster sauce, soy sauce, sake, chicken bouillon powder, sugar, and grated ginger. Mix well, until the meat turns into a sticky paste.
Once the meat is ground to paste, mix in the onions from Step 1.
Spread out the wonton wrapper and place the center with filling (about 1 ½ tbsp). Wrap and top with a green pea. Repeat the procedure until the fillings are gone.
Place parchment paper in a steamer and place the shumai. Steam for 10 minutes. (If you don’t have parchment paper, use nappa cabbage.)
Cook longer if the filling still looks raw. When you have finished steaming, the shumai should be plump and dense to the touch. Enjoy!