Wash and chop long beans into 1/2 inch size pieces,and peel and cube potatoes
Chop ginger and tomatoes into small pieces.
Heat oil in a pressure cooker and add cumin and mustard seeds.
When seeds start crackling add asafoetida and then add chopped tomato and ginger.Add salt and cook till tomato become soft .
Now add beaten curd and all the spices ,stir fry for a minute .
Add chopped beans and potatoes and stir for a minute .
Now add 3/4 cup water ,mix and pressure cook on medium flame for 2- 3 whistles or till cooked well (depending on the quality of vegetable)
let it cool down completely and then open and cook for few seconds.
Serve hot with roti or rice.