For the chicken:
1. Place the chicken in a bowl with the ginger, garlic, soy sauce, white pepper, Sichuan pepper and chilli.
2. Use your clean hands to mix everything together well.
3. Stir in the cornflour and egg whites, coating the chicken with it.
4. Leave to marinate for 30 minutes.
For the sauce:
1. Heat the oil gently and cook the ginger, garlic and star anise for 1 minute. Stir in the sugar, soy sauce, water, tomato purée, vinegar, mustard and teriyaki sauce, and cook simmering till the sugar has melted.
2. Add the hoisin sauce and cook for 5 minutes.
3. Add the sesame oil and remove from the heat.
4. Heat the oil in a wok and fry the chicken in small batches till golden and crisp but not cooked through.
1. Heat 1 tablespoon of oil in a large frying pan.
2. Add the chillies, garlic and 2 of the spring onions and fry for 3 minutes, stirring.
3. Add the chicken and spoon in the sauce.
4. Bring to the boil, toss the chicken into the sauce and stir to coat.
5. Stir in the remaining spring onions and coriander, and serve with sticky rice and extra soy sauce.
6. Serve on platters with sticky rice and additional soya sauce.