Heat oil in a pan and add mustard seeds.
When mustard pops up add onion and ginger . saute till onions becomes translucent
Add chopped chilli , salt, turmeric powder and mix well.
Peel potato and roughly mash. Add it into the pan and mix well.
Heat tawa and apply some butter. Add tortilla or roti and cook on both sides.
Apply mayonnaise and spread potato mixture.
Add some chat masala and roll it. Cook for 2 more minutes and serve hot