Place the coconut, fresh chillies and cumin seeds in a food processor with half the measurement water and blend to a fine paste.
Combine the mangoes with the turmeric, chilli powder and the remaining measurement water in a heavy saucepan. Bring to the boil, add the coconut paste and stir to mix well. Cover and simmer over a medium heat for 10–12 minutes, stirring occasionally, until the mixture becomes fairly thick.
Add the yogurt and heat gently, stirring, until just warmed through. Do not let the mixture come to the boil or it will curdle. Remove from the heat and keep warm.
Heat the oil in a small frying pan over a medium-high heat. Add the mustard seeds and as soon as they begin to pop (after a few seconds), add the dried chillies and curry leaves. Stir-fry for a few seconds until the chillies darken. Stir into the mango curry and serve immediately.