1. Place all the marinade ingredients in a bowl and marinate the chicken pieces for at least 20 minutes.
2. To prepare the sauce, heat the vinegar in a pan and add the sugar, light soy sauce, and tomatoe ketchup. Stir to dissolve the sugar, then set aside.
3. Preheated wok, heat 3 tablespoons of the oil and stir-fry the chiken until it starts to turn golden brpwn. Remove and set aside.
4. In the clean wok, heat the remaining oil and cook the garlic and gingerroot until fragrant. Add the vegetables and cook for 2 minutes. Add the chicken and cook for 1 minute. Finally add the sauce and sesame oil, then stir in the scallion and serve.