In a bowl add a strainer and then add curd in it.
Leave it to strain for 2 hours so that curd becomes thick.
After 2 hours transfer curd into a big bowl.
In same bowl add onions, cucumber, tomato, sugar, green chilli, coriander leaves, black pepper, sugar, salt and mix well.
Take bread slice of any shape and size.
Put this mixture between two pieces of bread to make a sandwich and press gently.
Heat pan on low flame and spread butter/oil/ghee on it.
Sprinkle some mustard seeds, put the sandwich on the pan and press gently.
Brush some butter/oil/ghee on the top part.
Turn sandwich over after a some time when bread become nice brown and crispy from down.
Cook until both sides turn crispy and golden brown.