Mix stock, cornstarch, soy sauce, sugar, garlic, ginger and red pepper in small bowl until smooth. Set aside.
Heat oil in large nonstick skillet on medium-high heat. Add chicken in batches; stir fry 5 minutes or until cooked through. Remove chicken from skillet. Add vegetables to skillet; stir fry 3 minutes until tender-crisp. Return chicken to skillet.
Stir soy sauce mixture. Add to skillet, stirring constantly. Bring to boil on medium heat; boil 1 minute or until sauce is slightly thickened. Sprinkle with sesame seed. Serve with cooked rice, if desired.