Preheat the oven to 400 F and line a large baking sheet with foil. Spray the foil lightly with cooking spray.
Mix the flour with the salt and pepper in a bowl.
Dip each piece of chicken into the beaten egg, then into the flour, coating it well. Place the chicken on the prepared baking sheet. Repeat with the remaining chicken.
Bake for 25 minutes, turning the chicken pieces about halfway through cooking.
Heat the sesame oil in a large frying pan on medium.
Add the garlic and ginger and fry for about a minute, stirring constantly.
Mix the corn starch and rice vinegar in a small bowl until there are no lumps. Add this to the pan, along with all the remaining ingredients.
Let everything cook for about 5 minutes, stirring frequently, until the marmalade has melted and the sauce has thickened.
Once the chicken is baked, add it to the sauce and stir well to coat.
Serve the orange chicken with rice, spring onions, and sesame seeds (if desired).