In a bowl, season chicken with salt and pepper.
Dredge chicken in flour, dip in beaten egg, then coat with cornstarch.
Heat oil in a deep pan over medium-high heat.
Fry chicken pieces until golden brown and crispy. Drain on paper towels.
In a saucepan, combine orange juice, zest, sugar, soy sauce, vinegar, garlic, ginger, and chili flakes.
Bring to a simmer, then stir in cornstarch slurry to thicken.
Add fried chicken to the sauce and toss until evenly coated.
Garnish with sesame seeds and green onions before serving.