To begin, cube the paneer into desired tikka size pieces. Dice the onion, tomato, and capsicum to match the size of the paneer cubes.
For the marinade, in a large bowl, mix together hung curd, ginger garlic paste, kala namak, Kashmiri red chilli powder, cumin powder, coriander powder, turmeric powder, crushed carom seeds, crushed kasoori methi, coarsely ground garam masala, gram flour, and lemon juice.
Heat mustard oil to the smoking point and add it to the marinade. Mix well.
Add in the vegetables first. Mix well. Next, add in the paneer pieces and mix until well coated. If you add in the paneer pieces first, they may crumble. Leave aside for atleast half an hour.
To assemble, thread the tikkas on a skewer alternating between the paneer cubes and the vegetables.
Grease the grill pan well with oil. Place the skewers and grill on all four sides until they colorize. Baste with a bit of oil for added flavor.
The Grilled Paneer Tikkas are ready to serve. Sprinkle a bit of chat masala on top and serve with mint chutney, onion rings, and lemon slices.