Marinate the fillets in 3 tablespoons of the fish sauce. Leave for 5 minutes.
Heat the oil in wok (ensure that the oil is no more than halfway up the wok). When very hot, about 350 degrees F, deep fry the fish until golden brown, about 5 to 6 minutes. Remove from the oil and drain on a paper towel-lined plate.
Make the salsa dressing by pounding the Thai chili peppers roughly with a pestle and mortar. Transfer the chilies into a salad bowl.
Season the dressing with fish sauce for saltiness, sugar for sweetness, and the lime juice for sourness.
Put the shredded mango, shallots, lemongrass, coriander and spring onions into the salad bowl and toss.
Serve the mango salad with the crispy fish.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.