Heat the oil, add mustard seeds and asafetida. When the seeds sputter, add the curry leaves and red chillies. Stir fry for a couple of seconds.
Add the cooked dal and enough water to get a fairly watery consistency. A dalitoy is typically quite thin, although you could make it thicker if you prefer it.
Bring the dal to a boil, lower the heat, and simmer another 10 minutes.
Add the coconut shreds and salt to taste.
Turn off the heat. Garnish with some fresh coriander, if you like.