Hello Yogesh!

Paneer sandwiches can be made in different ways. You can grate it with other ingredients (below mentioned) and toast it.

The other way is to cut paneer into small pieces and stuff with the ingredients like chopped onion, coriander leaves, chopped capsicum, bell peppers. Mix all the ingredients in Mayonese and spread evenly on the bread. Toast the bread. 

If you don't want to use mayonnaise, mix the ingredients in a bowl of hung curd and toast the bread on both sides. 

You can toast the sandwich in a grill or oven.