Place noodles in a medium-size pot with water just to cover. Add salt and bring to a boil. After boiling 1 to 2 minutes, transfer noodles to a colander and let cold water run through them for about 3 seconds. Drain and set aside.
Heat oil in a wok. When warm, add mustard seeds, chillies and lentils. Stir-fry until lentils are lightly toasted, then add peanuts and stir-fry for 10 seconds. Stir in coconut and fry it until light brown. Add cooked noodles and 1/4 cup water. Keep stirring over heat until well mixed, 10 to 20 seconds. Garnish with coriander and serve.