To prepare the squid, cut off the tentacles, and cut down the centre of the squid so it will open out flat. Score the inside with a crisscross pattern, then slice lengthways into
Marinate the squid strips and tentacles in the fish sauce and sugar for 30 minutes. Meanwhile, pound the coriander roots, salt and peppercorns in a mortar with a pestle, then add the garlic cloves and pound into a coarse paste, removing the garlic’s skin and hard base as you go.
Heat the oil in a wok or deep-fryer until smoking (180°C/350°F), and then toss half the squid in the flour until well coated. Shake away any excess. Deep-fry the squid, stirring regularly, until golden. Use a slotted spoon to remove the squid and drain on paper towel. Repeat with the remaining squid.
Scoop out any debris from the oil and then add the garlic mixture — be careful as it will spit. Move the garlic around the hot oil until it is golden, and then remove and drain on paper towel. Put the squid on a serving plate, sprinkle with the crispy garlic, white pepper and coriander leaves and serve with chilli sauce or Nam Jim.