In a small bowl add water and dissolve salt, put it aside.
Add the cold Clown Featherback Fish to the mortar.
Pound the fish into a paste. ( You can use a food processor), as needed, add the cold water with salt from the first step to ensure the fish remains sticky.
Transfer the fish paste into a mixing bowl. Add the rad curry, egg, sugar and fish sauce, Mix well
Add the chopped long beans and Kaffir lime leaves, stir until well combined.
Wet your hands and a tablespoon in the cold water, then scoop a heaping tablespoon of fish paste with the wet spoon and place in your hands. Gently pat the fish cakes to form into patties and place in a preheated wok
Heat oil in a wok, large heavy based frying pan or a deep fryer, to 350 degrees Fahrenheit. Add Thai basil and fry for 2-3 minutes until crispy. Take out and drain. Put to the side.
Deep fry the fish cakes in batches until golden. They will take between 3-5 minutes but check the first one before serving.
Serve the fish cakes on a bed of the fried Thai basil. Optionally, add a small bowl of cucumber relish.