In a small bowl, combine the marinade ingredients. Add chicken pieces and leave to marinate for 30-60 minutes.
Heat up oil in a wok over medium-high heat for frying. Heat to 350°F/180°C (use a kitchen thermometer)
Remove the chicken from the marinade and pat dry with paper towels. Coat each chicken piece in cornflour and add to wok and fry until golden brown. When done, remove the chicken and set to one side.
Pour used oil from wok and reduce heat to medium-low. Add the garlic, ginger, yellow onion, chili peppers. Cook for 2-3 minutes, stirring occasionally.
Add chicken pieces back to wok, along with green onion slices and Chinese 5-Spice. Cook for a further 2 minutes.
Remove from wok. Toss in pepper salt and serve.