Quarter the quails, remove the backbones and wing tips, clean the insides and pat dry with paper towel. Mix the Sichuan salt and pepper, sugar, soy sauce and shaoxing until the sugar dissolves, then add the quail pieces, toss together and marinate overnight.
Heat the oil in a wok or deep-fryer until just smoking (180°C/350°F). Coat each quail piece in flour, shaking away any excess, and deep-fry in batches until golden brown. Remove from the wok and drain on paper towel.
Arrange the quails on a plate and sprinkle with the combined spring onion, coriander, chilli and garlic. Serve with chilli sauce on the side.