If using corn on the cob, pick the corn kernals and add them to a bowl. Rinse and drain the water.
Boil them with little water until tender & drain completely. or Saute them in a tsp of butter or oil until tender.
Add red chilli powder (optional), cumin powder, chaat masala and salt. Mix and cool them.
Once cool add onions, tomatoes, green chilies, lemon juice and coriander leaves.
Transfer corn chaat to serving bowls and top with peanuts, sev or farsan. I did not have any so I fried paneer in little ghee until crisp and added.