Prep Time: 15 | Cook Time: 10-15 | Ready In: 25-30 + marinade time
For the marinade and sauce, place the chicken in a Ziploc bag; set aside. In a large saucepan, combine the chicken broth, orange juice, lemon juice,li hing powder, orange zest, vinegar, soy sauce, brown sugar, garlic, ginger; whisk until the sugar is fully dissolved. Measure out 3/4 cup of the mixture and pour it into the bag with the chicken; press out as much air as possible and seal the bag, making sure that all pieces are coated with the marinade. Refrigerate 30-60 minutes, but no longer.
Bring the remaining mixture in the saucepan to a boil over high heat. In a small bowl, stir together the cornstarch and cold water; whisk the cornstarch mixture into the sauce. Simmer, stirring occasionally, until thick and translucent, about 1 minute. turn off the heat, stir in the orange peel (if using); set the sauce aside.
For the coating, place the egg whites in a pie plate and beat with a fork until frothy. In a second pie plate, whisk together the cornstarch, baking soda and cayenne until combined. Drain the chicken in a colander or large mesh strainer; thoroughly pat the chicken dry with paper towels. Place half of the chicken pieces in the egg whites and turn to coat. Transfer the pieces to cornstarch mixture and coat thoroughly. Place the dredged chicken pieces on another plate or a baking sheet.
To fry the chicken, heat the oil in an 11- to 12-inch dutch oven or straight sided sauté pan with at least 3 qt. capacity over high heat until the oil reaches 350° on an instant read or deep fry thermometer. Carefully place half of the chicken in the oil; fry to golden brown, about 5 minutes, turning each piece with tongs halfway through cooking. Transfer to a paper towel lined plate. Return the oil to 350° and repeat with the remaining chicken.
To serve, reheat the sauce over medium heat until simmering, about 2 minutes. Add the chicken and gently toss until evenly coated and heated through