Place the Szechuan peppercorns in a dry wok and stir over a medium heat until they begin to pop and release their aroma. Transfer to a pestle and mortar and pound with the salt until coarsely ground.
Place the salt and pepper mixture, flours and chilli powder in a bowl and toss in the squid rings.
Pour enough oil for deep-frying the squid into a wok, and heat it to 190°C (375°F), or until a cube of bread dropped into the oil turns golden in 20 seconds. Add half the squid and deep-fry for about 1 minute until lightly coloured, then remove using a slotted spoon and drain on kitchen paper. Fry the remaining squid in the same way.
Place the chilli and spring onions in a slotted spoon and gently lower the spoon into the hot oil for a few seconds. Serve the squid with a scattering of coriander and the crispy chilli and spring onions.