Wash the chopped guaar 2 - 3 times in normal water. Microwave the beans in enough water for 10 mins, drain the beans and keep it aside.
In a non stick pan, heat cooking oil, add cumin and mustard seeds and allow to crackle.
Add green chillies and ginger-garlic paste, cook for 2 minutes on low flame.
Add chopped tomatoes, salt, red chilli powder, turmeric powder and mix well.
Cook for 3 - 4 minutes until nice color of tomatoes appear.
Add boiled beans and coriander powder, saute for 2 minutes.
Add 1/2 cup of water and garam masala powder, mix thoroughly. Simmer with lid covered so that the masalas are cooked and coats the vegetable.
Finally, add the dry mango powder, combine everything, make sure the subji is dry.
Sindhi Guaar is a dry Subzi, so cook till all the water is evaporated.
Serve hot with chapati.