Clean and devein the prawns. Marinate with salt and half the lemon juice.
Soak the basmati rice in water for 15 minutes. Wash several times to remove the starch and cook with 1 ½ times the volume of water to rice until fluffy. Cool.
Slice the onions. Heat oil and sauté until soft. Add the ginger, garlic pastes and sauté for another 2 minutes. Add chopped green chillies.
Wash and chop the herbs. Sprinkle over the cooked onion, ginger, garlic and turn off heat. Add salt to taste. Cool for 15 minutes.
Blend the onion and herb mixture in a food processor or mixer briefly to make a chunky paste.
Return the ground masala paste to the same dish as it was cooked in.
Drain the marinated prawns and add to the masala paste. Sauté for 1 or 2 minutes until the prawns curl up. Cool.
Mix the rice and prawn masala to finish the pullav. Taste and add lemon juice and more salt if necessary.