Cut the chicken breast or thigh into bite-size pieces.

Stir cornstarch, crushed red pepper flakes, soy sauce, vinegar, and broth or water in a small bowl.

Have your onion, garlic, ginger and green beans prepped and ready to go.

Heat 1 Tbsp oil in a large skillet over medium heat. Add onion slices and sauté for 2-3 minutes add garlic and ginger and cook for 2-3 more minutes.

Add green beans and cook, tossing often, until green beans are crisp-tender, about 4 minutes. Transfer green bean mixture to another medium bowl.

Heat remaining 1 Tbsp oil in same skillet over high. When oil is shimmering again, add chicken mixture and arrange pieces in a single layer in skillet. Cook, undisturbed, until chicken is browned and caramelized on first side, about 1 minute. Toss and continue to cook until meat is no longer pink and cooked through, about a minute or two longer.

Pour in sauce mixture and green bean mixture and cook, tossing briskly, until sauce is thickened and all ingredients are coated. Remove from heat and adjust seasonings as needed.