Take a wok, add oil and heat it.
Add mustard seeds, cumin seeds and allow them to splutter.
Add slit green chilies, dried red chilies, saute for few seconds.
Add the fresh curry leaves and let them crackle.
Add the finely chopped onions and cook them until they turn soft.
Add ginger garlic paste or use crushed ginger and saute for few seconds.
Add the cumin powder and turmeric powder, mix well.
Cook for few seconds.
Add the buttermilk and make sure the flame is on low heat while adding buttermilk.
Add chopped coriander leaves.
Switch off the flame after stirring well.
Serve hot with rice, chuney and pickle and pappadams.