Heat the oil in a heavy-based saucepan, add the onion and garlic and cook over a gentle heat, stirring frequently, for about 4 minutes or until softened. Stir in the curry paste and cook for a further 2 minutes.
Add the coconut milk and lime juice to the pan, stir to mix and simmer the curry sauce for 3 minutes. Add the ground almonds, prawns and salt to taste, then simmer the curry gently for a further 3 minutes until all prawns have turned pink and the sauce has thickened slightly.
Stir the diced mango into the curry and heat through for 1 minute. Taste and adjust the seasoning if necessary. Transfer the curry to a warmed serving dish, scatter over the chopped coriander and serve immediately.