In a mortar or food processor, make a thick paste (without adding water), using all the ingredients for the marinade.
Mix the marinade into the prawns making sure that all the pieces are well coated. Cover and set aside for 20 minutes.
Heat enough oil for deep frying in a deep pan or fryer.
While the oil is heating, beat 2 eggs in a bowl, and mix all the 3 flours with the seasoning in a separate shallow tray or bowl for coating. Make an assembly line starting with the marinaded prawns followed by the egg wash and finally the dry flour mix. This will allow you to fry quickly in an organised fashion.
When the oil is about 175℃, first, very carefully drop in the curry leaves and green chillies for a few seconds and remove. Drain and set aside for garnishing.
Then, dip each prawn lightly in the egg, coat on all sides with the flour mix and drop into the oil. Fry only a few at a time taking care not to overcrowd the pan. Fry the prawns for 2-3 minutes till crisp.
Arrange the hot prawns on a platter, sprinkle the curry leaves and fried green chillies over and serve.