Boil some water, turn off the gas and add green chillies to it. Leave them covered for ten minutes.
To make masala, dry roast methi dana and saunf till fragrant and dry
Add mustard seeds and roast them too. Turn off the gas and let the roasted spices cool down.
Grind to turn them into coarse powder. Add salt, some turmeric powder, Kashmiri chilli powder and hing. Combine everything well.
Now take out the green chillies from water. Keep the water for later use. When the chillies cool down, cut and make slits on them. Fill all the mirchis with the prepared masala.
Store it in an airtight container for up to 20 days.