Make the marinade by combining the soy sauce, sesame oil, garlic, ginger, and Chinese Five Spice powder in a large mixing bowl.
Add the chicken strips to the bowl and coat well with the marinade. Cover the bowl and let the chicken sit and absorb the marinade for about 10 minutes.
Heat the sesame oil in a deep skillet or work. Then sauté the marinated chicken strips for 5 minutes. Add the mushrooms, onions, cabbage and celery, and mix well. Keep cooking for 5-7 minutes, then add ginger and garlic. Stir once, then let it cook for 5-7 minutes more until everything is completely cooked through.
Stir well and add soy sauce, tossing to distribute evenly. Serve your keto moo shu chicken warm and sprinkled with sesame seeds.