1. Grind coconut with green chillies and mustard to coarse paste.
2. Heat the oil in a thick kadai. Add mustard.
3. When it splutters, add the dal and chillies.
4. When the dal is light brown, add curry leaves, asafoetida and onion. Fry till onion is golden brown.
5. Add spinach and cook till it is soft.
6. Crumble the potato and add to the kadai. Add ground paste and salt.
7. Keep covered on a low flame and cook for 5-8 minutes, stirring often.
8. Serve hot with chapathi or as a side dish for traditional lunch.

Note:
Spinach offers twice as much fibre as other greens