Rinse the crabs. Twist off and discard the aprons. Remove the upper shells of the crabs and reserve. Remove and discard the spongy gill tissue. Rinse the crab bodies and drain well. Cut each crab into half.
Heat the oil in a wok over high heat. Add the chillies and stir fry until they start to soften. Add the ginger, garlic, spring onion and peppercorns and stir fry until fragrant.
Add the crab and stir-fry for a minute. Add the shaoxing wine, soy sauce, sugar, vinegar and salt and stir-fry for a few minutes.
Add a little bit of water and cook until the wok is almost dry. Transfer to a plate and serve.
Shaoxing wine, sichuan peppercorns and black vinegar can be purchased in Chinese/Oriental speciality shops.