In a bowl, toss chicken pieces with cornstarch until evenly coated.
Heat sesame oil in a pan over medium heat. Add chicken and cook until golden brown and cooked through, about 6-8 minutes.
In a small bowl, whisk together soy sauce, honey, rice vinegar, garlic, ginger, and water (if needed).
Pour the sauce mixture over the chicken and cook until the sauce thickens, about 2-3 minutes.
Sprinkle sesame seeds and green onions over the chicken before serving.