Heat oil in a pan. Add chopped onion and stir till light brown.
Add chopped boiled potatoes and put salt, turmeric powder and chopped green chillies.
Put garam masala powder and mix well
Take a kulcha and spread this potato mix on it.
Cover this whole with another kulcha.
Spread butter in outer surface of the kulchas.
Grill the kulcha sandwich on a grill plate till golden brown.
Serve hot with tomato sauce.
