Heat oil in a pan, add mustard seeds, cumin seeds and hing.
Add the chopped green chillies and mix.
Add the finely chopped onion and cook well.
In a mortar and pestle or grinder, pound the garlic and red chili powder to make a paste. You can add a little water if needed.
Add the garlic-chili paste to the pan and cook the paste.
Add coriander powder, cumin powder, salt and garam masala. Mix well.
Add the chopped coriander and switch off the flame.
Add 1-1.5 cups of yogurt (dahi) and mix well.
Serve hot.
