First clean & wash the fish. Rinse and pat dry. "Butterfly" the fish ( split fish using sharp knife). Rub salt all over fish. Coat fish with cornflour on both sides, inside of meat and outside of skin
Deep fry fish on medium heat until crispy and golden brown, about 5 minutes on each side. When done, set the fish aside.
Prepare the ingredients for the sauce. Chop bird's eye chilies and coriander leaves, slice thinly shallots and red chili, squeeze the juice from kaffir lime, measure the sugar and fish sauce.
Mix all the sauce ingredients together in a bowl. Adjust taste if needed.
Shred coarsely cucumber and slice kafir lime into thin pieces for garnishing the fish.
Line a plate with shredded cucumber. Top with the fried fish. Then pour the sauce over the fish. Garnish with kaffic lime slices and coriander leaves. And you're done! Serve immediately.