Heat oil in kadai and temper with mustard, urad dal and curry leaves.
Once it browns add the finely chopped onions and saute for a minute
Then add chopped cluster beans and saute for 2 mins.
Then add salt, turmeric powder and sambar powder.
Mix and add water
Close the lid and cook till and allow it to cook.
Cook till it is soft and all water evaporated.
Then add grated coconut, mix and switch off the flame.
Cluster beans poriyal is ready.
Notes
You can add curry masala or red chilli powder and coriander powder or green/red chilli instead of sambar powder. You can skip coconut too. but it is recommended for good flavor and taste.