Cut chicken breast into 1/2-inch cubes, set aside.
To make marinade - combine egg white, salt and sugar in a bowl and stir vigorously until ingredients are thoroughly mixed. Add chicken cubes to marinade and stir to coat well.
To make orange sauce - combine water, ketchup, sugar, vinegar, soy sauce, 4 teaspoons cornstarch and sesame oil; stir and set aside. Place a pot over high heat. When pot is hot, add the 2tablespoons vegetable oil and heat. Add orange peel and scallion and stir for about 20 seconds, taking care not to burn the orange peel.
Pour combined sauce ingredients into the pot and cook, stirring frequently, until sauce has thickened, about 12-15 minutes.
Preheat 4 cups oil to 350-375°F. Meanwhile, put marinated chicken in the plastic baggie containing the cornstarch. Shake chicken well for about 20 seconds or until chicken is covered with cornstarch. Shake off all excess cornstarch and fry chicken in hot oil until golden brown, approximately 2 1/2 minutes. Remove chicken from oil with a slotted spoon, drain well and set aside. Add fried chicken to pot with heated orange sauce, stir for about 30 seconds, and then serve immediately.