Method

1. To make the chilies in fish sauce, place the chilies, shallot and garlic (if using) in a bowl and pour over the fish sauce. Leave to steep – the longer, the better, as the heat becomes quite mellow with time. If using the lime juice, squeeze it in just before serving.
2. Rinse the fish then pat it dry with paper towel. Score the fish by making several diagonal cuts into each side, going almost to the bone. I like to score quite finely, others don’t – it’s up to you.
3. Pour the deep-frying oil into a large, stable wok or a wide, heavy-based pan until it is about two-thirds full. Heat the oil over a medium–high flame until a cooking thermometer registers 180°C Alternatively, test the temperature of the oil by dropping in a cube of bread – it will brown in about 15 seconds if the oil is hot enough
4. Meanwhile, marinate the fish in the fish sauce and sugar for about 5 minutes (fillets will need less time – just a minute or two), turning it once or twice.
5. When the oil is ready, shake off the excess fish sauce and deep-fry the fish, carefully turning it once or twice to ensure even colouring and cooking.
6. Depending on the size and thickness of the fish, it can take as long as 10 minutes, but be careful not to burn the fish as it takes on a deep golden colour.
7. Once cooked, remove the fish from the oil and drain on paper towel. Place on a plate and sprinkle with chopped coriander.
8. Serve with steamed rice and a bowl of the chilies in fish sauce.