Add boiled potato, onion, coriander leaves, green chilli, chat masala, salt and mix this well in a bowl. Cut the egg into two portions.

Take a bread slice spread the tomato ketchup. Take another bread slice put the half egg into the centre and spread the potato mixture. Now cover this potato bread with another slice of bread, to which ketchup have been applied.

Applied butter and put this on a tawa or grill the sandwich till browned from both sides. Cut into square and serve with tomato ketchup.