Mix the teriyaki sauce and scallions. Marinate chicken in it for 60 minutes minimum.
Save marinade for later and take the chicken out.
Pour the oil into a large frying pan and heat up on high flame.
Fry the onions for 2 minutes. Pour chicken in and fry while stirring for 2 minutes.
Pour in the reserved marinade and wheat free tamari sauce and cook for another 10 minutes.
Add in the xanthan gum and cook until it becomes a bit thicker. Serve hot.