Add the chili pepper and tangerine peel to the remaining oil in the pan. After 15 seconds stir-frying over high heat, return the chicken to the pan. Turn the chicken completely over once. Mix the rest of the sherry and soy sauce, the vinegar, sugar, and pepper in a bowl; pour evenly over the chicken. Stir-fry for a further 1/2 minute, sprinkle with sesame oil, and serve.