Hang curd in a muslin cloth or in a fine strainer to drain water from it, for at least 4 hours.
For Masala Gravy:
Prepare masala gravy separately. Heat oil in a pan, add mustard seeds and temper.
Add salt, turmeric powder, red chilli powder, garam masala, kasoori methi powder and cook for a minute.
Add chopped onion, tomato, green chilli, chopped ginger, chopped coriander and crushed whole spices.
Saute till masala gets dry and thick.
Add hung curd and mix well.
Garnish with chopped curry leaves, fresh coriander and fried whole red chillies.
Serve luke warm with rice or roti.