Mix the sauce ingredients together and set aside.
Mix the chicken with the soy sauce and sherry and set aside.
Prepare all the vegetables, including garlic and ginger, and set aside, leaving in small piles on your cutting board or on a large plate.
Mix the cornstarch and the chicken broth in a small bowl and set aside.
Once everything's ready, pour 1 Tbs of the oil in deep skillet and heat over high. Add half the chicken and stir fry 2-3 minutes, until just done. Remove to a bowl and then stir fry the other half of the chicken.
Add the remaining oil (2 Tbs) to the skillet and cook the onion until browned slightly but still a bit crisp (1 minute or so). Add the garlic and ginger. If you were doing a different combination of vegetables and some took longer to cook you might add the longer cooking ones now. (E.g. asparagus, snow peas, cabbage, peppers, and celery all take a bit longer to cook than mushrooms, water chestnuts, green onions, or shredded carrots. ) Cook another minute or two, stirring frequently.
Add any other vegetables to the pan (or all of them in my case!) and cook another minute or two, until crisp but tender. Return the chicken to the pan and stir it in.
Add the sauce and stir to coat. Add the cornstarch and chicken broth mixture and stir until everything is warm and the sauce looks a bit shiny and delicious! If it seems too thick, you can add a bit of water or chicken broth.