Season chicken with salt and pepper, then toss with cornstarch until lightly coated.
Heat oil in a large skillet over medium-high heat. Cook chicken for 6–8 minutes, turning occasionally, until golden and cooked through.
In a small bowl, whisk honey, soy sauce, vinegar, ginger, and water.
Add garlic to the skillet and cook for 30 seconds. Pour in the sauce.
Reduce heat to medium and cook for 2–3 minutes, stirring until the sauce thickens and coats the chicken.
Garnish with sesame seeds and green onions, if desired. Serve hot with rice and vegetables.