Wash hands with soap and water.
Scrub the onion with a clean vegetable brush under running water. Cut onion into thin wedges.
Scrub baby carrots with clean vegetable brush under running water. Cut carrots lengthwise in half.
Gently rub broccoli flowerets under cold running water.
Gently rub mushrooms under cold running water. Dice the mushrooms.
Scrub red bell pepper with clean vegetable brush under running water. Dice the red bell pepper.
Heat vegetable oil in skillet over medium-high heat. Add chicken, garlic and gingerroot; stir-fry 2 to 3 minutes or until chicken is brown.
Wash hands with soap and water after handling uncooked chicken.
Add onion, carrots, 3/4 cup of the broth, the soy sauce and sugar. Cover and cook over medium heat 5 minutes, stirring twice.
Add broccoli, mushrooms and bell pepper. Cover and cook about 5 minutes, stirring occasionally, until chicken is no longer pink in center and internal temperature reaches165°F on food thermometer, and vegetables are crisp-tender.
Mix cornstarch with remaining1/4 cup broth; stir into chicken mixture. Cook, stirring frequently, until sauce is thickened. Serve over noodles or rice.