Crumble idlis and set aside.
Heat oil in a frying pan and add mustard seeds, cumin seeds and asafoetida.
When the mustard seeds splutter, add onions and sauté till onions turn light brown.
Add curry leaves, chopped ginger and green chillies and saute for few seconds.
Add carrots, beans and little water and close the pan. Let the veggies cook till they are soft.
Add crumbled idli and mix well.
Remove from the stove. Add lemon and mix.