Season chicken pieces with salt and pepper. Toss with cornstarch until evenly coated.
Heat oil in a large skillet over medium-high heat. Cook chicken in batches for 6–8 minutes, turning occasionally, until golden and crispy. Remove and set aside.
In the same skillet, combine all sauce ingredients except the cornstarch slurry. Bring to a simmer over medium heat.
Stir in the cornstarch slurry and cook for 1–2 minutes, until the sauce thickens and becomes sticky.
Return the chicken to the skillet and toss to coat in the sauce until glossy and heated through.
Garnish with sesame seeds and green onions. Serve with steamed rice or vegetables.