Cut your skinless/boneless white fish into 4cm x 1cm pieces. Pat dry to remove any moisture.
In a mixing bowl, combine the lemon juice, ginger, garlic, mustard paste, turmeric, chilli, asafoetida, carom seeds and salt to taste. Taste the marinade and adjust salt as necessary.
Add the fish to the marinade and coat evenly. Set aside for 20 minutes.
Heat oil to 160°C. Add the chickpea and rice flours to the marinated fish and let it form a thin coating around the fish
Deep fry the fish in batches until golden brown (upto a minute on each side). Transfer on paper towel to get rid of excess oil.
Sprinkle chaat masala and serve hot with lemon wedges.
