Place coriander, cumin seed and chilli flakes in a dry pan and toast until golden. Remove and crush in a mortar and pestle. Rub over the prawns with some Olive oil to create a spice crust. Reserve.
Now for the sauce, heat the oil in a frying pan; add onions with a pinch of salt to help the moisture release. Next add the curry leaves and green chillies.
Cook and stir until the onion is soft, then add the turmeric ginger and garlic. Pour in the coconut milk, sugar and salt. Bring to a simmer and cook for 3 minutes.
Sear the spice coated prawns for about a minute each side, sprinkle with salt then slip into the sauce.
Serve with crusty bread for starter.