Peel and devein the prawns, wash thoroughly and pat dry.
Marinate the prawns in ginger garlic paste, 1/2 tablespoon Kashmiri red chilli powder, coriander powder, 1 tablespoon lemon juice and salt for 15-20 minutes.
Squeeze out the extra moisture, add all-purpose flour, gram flour/besan, 1/2 tablespoon Kashmiri chilli powder, rest of the lemon juice, yoghurt and 1 teaspoon of oil.
Mix all the spices with the marinated prawns.
Prepare oil for deep frying, making sure to maintain the temperature at medium high.
Add one prawn initially in the hot oil to check if it is sufficiently hot.
Add the marinated prawns in the hot oil in batches, and fry till they turn a rich golden brown on both sides.
Arrange the marinated prawns on an aluminium foil in a baking tray, drizzle a little oil on the prawns, and broil on high, 5 to 7 minutes on both sides or until they turn a light golden brown.
Sprinkle chaat masala on top, serve with green chutney or ketchup.