For preparing onion - prawn pickle, clean the prawns. Marinate the prawns for 10 minutes with turmeric powder, 1 tsp vinegar and salt.
Fry the prawns in oil and keep it aside.
In the same oil fry onions, ginger, garlic, curry leaves and green chillies.
Add in prawns and fry it well.
Add in salt, vinegar and rest of the ingredients. Fry well and then allow it to cool.
Allow it to cool and store in a bottle.
Onion - prawn pickle is ready. Serve when required.