Heat oil in a pan.Splutter mustard seeds and fenugreek seeds.Add chopped onion and saute till they start to change colour.Now add crushed ginger garlic,sliced green chilli and curry leaves.Saute till the raw smell goes.Now add chopped tomato and let it cook well and become soft.Now add in the spice powders.Mix well.Add enough salt.Add 1/2 cup of water.

Cover and cook for 3-4 minutes.Then add thick coconut milk and let it cook for another 3-4 mints.The gravy will become creamy and thicker.Switch off the flame.

In another pan heat some oil.Add sliced small onion and let it become golden brown.Then add dry red chilli and curry leaves.Roast them slightly.Pour this tempering into the prawn curry.

Cover the lid and let it sit for 5 mints.Enjoy with steamed rice or appam.