Using a manual slicer or a food processor fitted with shredding disk, finely shred carrots. Mince chilies. In a heavy skillet heat oil over moderate heat until hot but not smoking and cook mustard seeds, chilies, asafetida, and curry leaves, stirring constantly, until mustard seeds begin to pop. Stir in carrots until coated well and transfer to a bowl. Toss salad with lemon juice and salt to taste. Salad may be made 1 day ahead and chilled. Covered. Before serving, add additional lemon juice to taste. Serve salad warm or at room temperature.