Peel, de-vein and rinse the prawns. Mix them with salt to taste, 1 tsp of the turmeric and half the lime or lemon juice, and leave to marinate for 10-15 minutes.
Meanwhile, heat the oil in a pan until hot and add the mustard and cumin seeds. Once they begin to pop and splutter, add the curry leaves, garlic, ginger, chilli, lime leaves and shallot. Reduce the heat slightly and cook until the shallot becomes translucent. Now add the remaining turmeric and stir-fry for a few seconds, then add the stock, bring to the boil and cook for three to four minutes, until it has reduced. Now add the passata, chilli powder and sugar. Reduce further until it has a consistency you like, then add the coconut milk and coriander, taste, adjust the seasoning and simmer for five minutes or so.
Remove the sauce from the heat and pass through a fine sieve, then return it to the pan. Bring to a simmer over a gentle heat, then add the prawns. Cook on a low heat for five to seven minutes, until the prawns turn pink and are just cooked. Finish off with the remaining lemon or lime juice and sprinkle with coriander to serve.
Recipe courtesy of Reza’s Indian Spice by Reza Mahammad, published by Quadrille (£17.99, hardback). Photos © Martin Poole.