Slice chicken thinly and marinate it with soy sauce, garlic, and ginger for about 15–30 minutes until slightly glossy and fragrant.
Heat a wok or skillet over medium-high heat until hot and lightly smoking for proper searing.
Add sesame oil and cook chicken for 6–8 minutes until golden brown edges appear and juices mostly evaporate.
Remove chicken and sauté onion, bell pepper, and broccoli for 5–7 minutes until slightly crisp and vibrant in color.
Return chicken to the pan and stir everything together until evenly combined and lightly sizzling.
Add rice vinegar, honey, and chili flakes, stirring for 2–3 minutes until sauce begins to coat ingredients.
Pour in cornstarch slurry and simmer for 2–3 minutes until sauce thickens and becomes glossy.
Taste and adjust seasoning with salt or soy sauce, then turn off heat once everything is well coated and aromatic.