In a medium saucepan, combine orange juice, sugar, rice vinegar, soy sauce, ginger, garlic, and red chili flakes. Cook for about three minutes on medium heat, stirring occasionally until well blended and bubbly.
In a separate bowl, mix two tablespoons of cornstarch with two tablespoons of cold water to form a paste. This will be your thickening agent.
Add the cornstarch paste to the orange mixture in the saucepan and cook until thickened, about five minutes. Remove from heat and stir in the orange zest.
In a shallow dish, combine flour, cornstarch, and a pinch of salt. Mix well.
In another bowl, whisk the eggs until combined. Dip each piece of chicken in the egg mixture and then coat with the flour mixture.
Pour 2-3 inches of oil into a skillet and heat over medium-high to 350°F. Carefully add the chicken to the hot oil and fry until golden brown, about two to three minutes.
Remove the fried chicken and let it drain on paper towels. Repeat with remaining pieces.
Toss the fried chicken in the warm orange sauce until well-coated.
Garnish with green onions and additional orange zest before serving.