First you need to make the chicken wonton filling. Combine the chicken with half the soy sauce, all the cornstarch, half the green onions and all the cabbage.
Put a teaspoon of this mixture in the middle of each wonton wrapper and fold the wonton wrappers in half lengthwise so the ends touch.
Press down firmly on the ends to seal the wontons and use your thumbs to push out the air. Fold the wonton edges over one more time, and with wet fingers press them sealed.
You can freeze them at this point (for up to 2 weeks) and then thaw.
Bring the chicken broth to a boil and then turn down the heat. Add the rest of the sliced onion and soy sauce, then add the wontons with a spoon, making sure you don't break any.
Let them simmer for 5 minutes, then add the green onion and peas (if using) to the soup, cook 1 more minute and serve.
