Using a small sharp knife, split the squid’s body in half. Remove the transparent bony section.
Wash the halves thoroughly under cold running water and then pull off and discard the skin.
Cut the tentacles from the head, cutting just above the eye.
Cut the squid meat into 3.5cm/1½in strips.
If you are using fresh peas, blanch them for three minutes in a large pan of boiling salted water, drain and set aside. If you are using frozen peas, simply thaw them and set them aside.
Heat a wok or large frying-pan over high heat until it is hot. Add the oil, and when it is very hot and slightly smoking, add the garlic and stir-fry for one minute, or until lightly browned. Remove with a slotted spoon and drain on kitchen paper.
Add the squid to the pan and stir-fry for one minute.
Tip in the shallots, chillies, peas, fish sauce, oyster sauce and sugar and continue to stir-fry for three minutes.
Add the basil and give one last stir. Turn the mixture onto a platter and garnish with the reserved fried garlic.