In a large bowl, combine both types of flour with the chilli powder, sea salt and Szechuan pepper. Add the squid and toss to coat, shaking off any excess flour.
Fill a wok with oil to about a third full (about 2 cups) and heat until the surface seems to shimmer slightly.
Add half the squid and deep-fry it for between 45 seconds and 1 minute, or until it’s just tender and beginning to colour. Remove with a slotted spoon and drain well on kitchen paper. Repeat the process with the remaining squid.
Arrange the lettuce leaves on a platter and top with the squid. Garnish with finely chopped spring onions and serve with the lemon wedges.