Grind coconut, red chillies and cumin to a coarse paste.
In a kadai add the oil and when it is hot add mustard seeds. When the mustard seed pops up add asafoetida and curry leaves. Fry the contents for a while.
Add beans pieces along with salt and mix well. Sprinkle a handful of water on the beans. Cover with a lid and cook till the vegetable is soft and all the water is absorbed.
Add ground coconut paste and stir well and remove from stove.