Cook the dal with enough water, salt and turmeric powder till very soft. Mash the dal well to break up the lumps and get a smooth consistency.
Blend grated coconut, green chilli, garlic and jeera with just enough water to get a fine, thick paste like consistency.
Return the mashed dal to heat, add the ground coconut paste and mix well. Bring to boil; taste and season with salt if necessary. Cook till the rawness of the coconut disappears; the final consistency of the dal must be slightly thick and not too watery.
In another small pan, heat coconut oil and add the mustard seeds. When it begins to crackle, add the dry red chillies and fry on low heat for 5 seconds. Pour over the cooked dal and keep it covered for at least 10 minutes before serving.