Cut the chicken breast into 1/2 inch cubes; set aside.
Combine the egg white, salt, and sugar in a bowl and stir vigorously until the ingredients are thoroughly mixed. Add the chicken cubes to the egg white mixture and stir to coat well.
To make the orange sauce, combine the water, ketchup, sugar, vinegar, soy sauce, 1 tablespoon plus 1 teaspoons cornstarch, and sesame oil; stir and set aside. Place a pot over high heat. When the pot is hot, add the 2 tablespoons vegetable oil and heat. Add the orange zest and green onions and cook, stirring, for about 20 seconds, taking care not to burn the orange zest.
Pour the combined sauce ingredients into the pot and cook over medium heat, stirring frequently, until the suace has thickened, 12 to 15 minutes.
Preheat the 4 cups oil to 350°F in a deep-fryer.
Meanwhile, put the coated chicken in a resealable plastic bag containing the 1 cup cornstarch. Shake the chicken well for about 20 seconds, until the chicken is covered with the cornstarch. Shake off all the excess cornstarch and deep-fry the chicken in the hot oil until golden brown, about 2 1/2 minutes. Remove the chicken from the oil with a slotted spoon, drain well on paper towels, and set aside. Add the fried chicken to the pot with the hot orange sauce, stir for about 30 seconds, then serve immediately.