Heat oil in a pan.
Splutter mustard seeds.
Add curry leaves, turmeric powder, green chillies and sliced onions.
When onions turn brown, add boiled potatoes and salt along with a cup of water.
Allow it to boil for 5 mins.
Remove from flame and keep it aside.
Mix well together the eggs, green chillies, milk, coriander leaves, curry leaves and salt. Keep it aside too.
Heat a dosa tava.
Pour a ladle of dosa batter on it and make dosas.
On top of it, pour 3 tbsp of egg mix and spread it well.
Apply some ghee if desired.
Turn the side to cook the egg well.
Turn it back and add the masala mix to it and fold it like masala dosa.
:- Serve hot with chutney or sambhar.