Marinate the fish cubes in vinegar for twenty minutes. Remove from the vinegar and pat them dry.
Make a batter of gram flour, yogurt, egg, carom seeds, salt, lemon juice, red chilli powder, ginger paste and garlic paste.
Keep the fish cubes in this marinade for about twenty minutes. Heat sufficient oil in a kadai and deep-fry the fish till golden brown and crisp.
Drain on absorbent paper. Serve hot, sprinkled with chaat masala and lemon wedges.