For the Kerala prawns, heat a large wok over a high heat. When the wok is hot, add the oil and heat until just smoking.
Add the mustard seeds and curry leaves and stir-fry for 2-3 minutes, or until the seeds start to pop. (CAUTION: Popping seeds can be dangerous. Cover the pan with a lid and keep the pan well away from the eyes and face.)
Add the spices and stir well. Continue to fry for a further minute, then add the tamarind paste, chillies and ginger and stir-fry for a 1-2 minutes.
Add the onion and fry until pale golden-brown, about 2-3 minutes.
Add the garlic and stir-fry for a further 20 seconds.
Add the prawns, stir well to coat them in the spice mixture, then continue to stir-fry for a further 4-5 minutes, or until the prawns are cooked through. (NB: The prawns are cooked through when the flesh is pink.)
Stir in the sliced coconut, lime juice and coriander leaves until well combined, then season, to taste, with salt and freshly ground black pepper. Heat through for one minute.
To serve, divide the Kerala prawns equally among four serving plates. Spoon the steamed rice alongside.
