Cut chicken into 1/2 inch strips; place in a resealable plastic bag. Add cornstarch & toss to coat. Combine soy sauce, ginger & garlic powder; add to bag & shake well. Refrigerate for 30 minutes.
In a large skillet or wok, heat 2 tbsp. of oil; stir-fry chicken until no longer pink, about 3 – 5 minutes. Remove & keep warm. Add remaining oil; stir-fry broccoli, celery, carrots & onion for 4 -5 minutes or until crisp-tender. Add water & bouillon. Return chicken to pan. Cook & stir until thickened & bubbly.