I make this in a pressure pan and so this is ready in no time. A perfect hit with sambar and dali saar alike.
Heat oil in a pressure pan. Add the urad and chana dals, mustard seeds and asafoetida. When the mustard splutters, add the curry leaves and the red chillies. Fry for a minute. Add the chopped beans and the salt along with a little water. Cover and cook for one whistle.