Wash and cut the brinjals in thin circular slices. Smear with salt, turmeric and chilli powder. Keep aside for sometime.
Mix well the slightly coarse gram flour, rice flour, salt, chilli, turmeric and sodium bicarbonate. Add enough water to make it a thick batter. Add the coriander leaves and 2 tbs of hot oil. Mix it well.
Grind the raw prawns in the mixie. Squeeze the grated onions. Mix it with the other ingredients for filling.
Take two same sized brinjal slices. Sandwich with the filling. Do not overstuff. Press the sandwich lightly to fix. Heat enough oil in a pan for deep frying. Dip the sandwiches in the prepared batter and fry till golden and puffed up. Turn over once in between. Serve hot with chutney or ketchup.