Heat a wok until just smoking. Add the vegetable oil and, when hot, add the chillies and chicken, spreading them evenly around the wok. Leave undisturbed for about 1 minute, allowing the chicken to brown. Then start to stir-fry the chicken until it has browned all over and the chillies have blackened. Add the snow peas to the wok and stir-fry for a further 30 seconds, then remove the chicken, chillies and snow peas from the wok.
Add the spring onions, ginger, garlic and Sichuan pepper to the wok and stir-fry for 15 seconds, then deglaze with the shaoxing. Return the chicken, chillies and snow peas to the wok, along with the salt, white pepper, soy sauce, vinegar, sesame oil, sugar and chilli oil. Stir-fry for a further 30 seconds and then discard the chillies to serve.