Put the garlic, ginger, ground coriander, cumin, chilli powder, paprika, turmeric and jaggery or sugar in a large wok. Pour in the measurement water and stir to mix well. Place the wok over a high heat and bring the mixture to the boil. Reduce the heat and cook, covered, for 8–10 minutes.
Add the mango, coconut milk and tamarind paste and stir to combine. Bring the mixture back to the boil, then add the prawns.
Stir reduce the heat and simmer gently for 6–8 minutes. Tear some of the coriander leaves into the curry (reserve the rest to use as a garnish) and cook for another 2 minutes until the prawns have turned pink and are just cooked through. Season with a little salt and serve immediately with steamed basmati rice, garnished with the reserved sprigs of coriander.