Heat a non stick pan with cooking oil, saute onions, then add all the spices along with tomato. Let till the tomato becomes soft.
Then, add the cooked corn, potato and mash everything well. Cook till the masala becomes dry. Keep it aside.
Trim the bread slices on sides and toast it with ghee on both sides.
On the top, place the cheese slices, then top with stuff and press the other slice over it. Cook on both sides for 2 seconds, remove and serve with ketchup.