Optional garnishes: thinly sliced green onion and sesame seeds
Place flour in a large resealable plastic bag. Season chicken with salt and pepper. Add to bag, a few pieces at a time, and shake to coat. In a large skillet, cook chicken in oil in batches over medium heat until chicken is no longer pink. Remove and keep warm.
In the same skillet, combine the remaining ingredients. Bring to a boil, stirring to loosen browned bits from pan; cook and stir until thickened. Return chicken to the pan; heat through. Sprinkle with green onion and sesame seeds if desired.