Kerala prawn curry (Chemmeen curry)

1. Peel and devein the prawns and rub them with a pinch of turmeric and salt. Soak the kokum in a little lukewarm water.

2. Heat the coconut oil in a pan, add the mustard seeds and, when they start to pop, the curry leaves: careful, it spatters!

3. Add the thinly sliced onion and fry for 6 minutes until soft, then the ginger, garlic and green chillies, halved lengthways, and fry for 1 more minute.

4. Over low heat add the remaining turmeric and the chilli powder, stir for 30 seconds, then add the diced tomato and cook for 4 minutes.

5. Pour in the coconut milk, add the kokum with its soaking water and simmer for 5 minutes (don't boil hard or the coconut milk will split). Add the prawns and cook for 4-5 minutes until pink.

6. Serve with steamed rice or appam.

Tip: Chemmeen means prawn in Malayalam. Kokum gives Kerala curries their typical tang; you can replace it with a teaspoon of tamarind paste. Don't overcook the prawns or they'll turn rubbery.