Rinse the fish and pat dry. Using a sharp serrated knife, make 3-4 vertical cuts along each side
Squeeze about 1 Tbsp. of lime juice over the fish, then sprinkle with salt to season. Be sure to do both sides. Set aside while you prepare the sauce.
Place all sauce ingredients in a food processor or mini-chopper and process until you have a beautiful bright green paste-like sauce.
Taste-test the sauce, adding more fish sauce if not salty enough, more sugar if too sour, or more chili/chili sauce if not spicy enough.
Pour sauce into a sauce pan and set aside until later. Spread flour over a plate or other clean surface. Then dredge the fish in it, turning until it's well coated.
Pour enough oil into a wok or large frying pan (large enough for the fish) so that oil is at least 1 inch deep. Turn heat on high. When you see bubbles forming on the bottom of the pan, test it by dropping in a small cube of bread - if it begins to sizzle and turn brown, it's ready. If not, the oil needs longer to heat up. When hot enough, carefully place fish in the oil. Turn the heat down to medium, or just above medium.
Allow fish to cook for at least 2 minutes per side before disturbing or turning it (this will prevent the skin from tearing). Depending on how thick your fish is, it will take 6/8 minutes to cook. Fish is done when the skin is golden-brown and the flesh inside the cuts is white and opaque.
Turn off the heat and remove fish from oil. Set it on the paper towel to drain and crisp up. Meanwhile, place sauce over medium heat for a minute or two - just until warm enough to serve.
Tip: Don't overheat. If you boil the sauce, you will lose its wonderfully fresh flavour!
To serve, place fish on a large plate or platter, and pour the sauce into a small bowl. Garnish with slices of tomato and/or cucumber, plus a few sprigs of coriander and basil.