In a medium saucepan over medium heat, combine orange juice, sugar, rice vinegar, soy sauce, ginger, garlic powder, and red chili flakes. Stir well and bring to a gentle simmer for about 3 minutes.

Make a cornstarch slurry by whisking together cornstarch and cold water. Slowly pour this into the simmering sauce while continuously stirring. Cook for another 5 minutes until thickened.

Set up a dredging station with one dish for the cornstarch, flour, and salt mixture, and another for whisked eggs. Coat chicken pieces first in egg, then in flour mixture.

Heat neutral oil to 350°F. Fry chicken pieces in small batches for 2-3 minutes until golden brown. Drain on paper towels.

Transfer fried chicken to a bowl, pour the sauce over, and toss gently. Garnish with green onions and serve warm.