1.Make nam jim. Blend or process ingredients until almost smooth. Season to taste with extra fish sauce, sugar or juice, as required.
2.Rub oil over salmon; season. Heat a medium frying pan over high heat; cook salmon, skin-side down, for 5 minutes or until skin is crisp, pressing down with a spatula to prevent curling. Turn salmon; cook a further 1 minute or until cooked as desired.
3.Meanwhile, using a vegetables peeler, cut cucumber lengthways into ribbons. Combine cucumber, radish and coriander in a small bowl.
4.Serve salmon with cucumber salad and nam jim.
Coriander is one of the few fresh herbs to be sold with its root attached. It should be readily available from greengrocers. Asian greengrocers will certainly stock it. Remove the salmon from the pan when it is still a little rare in the centre as it will continue to cook on standing.