Cut the chicken breast into small cubes. Crack the eggs into a bowl and beat them well. Add the chicken cubes to the eggs and let them sit for 10 minutes.
In a separate bowl, mix the all-purpose flour, cornflour, and salt. Drain the chicken pieces from the egg mixture and coat them in the flour mixture, ensuring each piece is evenly covered. Shake off any excess flour and place the coated chicken on a plate.
Heat the sunflower oil in a small deep frying pan. Once the oil is hot, fry the chicken pieces on high heat for about 3 minutes or until golden brown. Remove the chicken from the oil and place them on a plate lined with absorbent kitchen paper to remove excess oil.
To prepare the orange sauce, combine the orange juice, sugar, rice vinegar, soy sauce, sesame oil, garlic powder, ginger, and chili flakes in a pan. Heat the mixture until it starts to warm, then reduce the heat and simmer for 3 minutes.
In a small bowl, dissolve the cornflour in water and add it to the sauce. Stir in the orange zest and continue to cook for another 2 minutes or until the sauce thickens.
Add the fried chicken to the sauce, stirring well to ensure the chicken is fully coated in the sauce. Serve the chicken sprinkled with sesame seeds and chopped green onions. For a complete meal, serve with boiled basmati rice if desired.