1.Blend or process tomato, chopped coriander, garlic, ginger, chilli and spices until mixture forms a smooth paste.
2.Shell and devein prawns, leaving tails intact.
3.Heat half the oil in large frying pan over medium heat; cook onion and curry leaves, stirring, until onion is soft. Increase heat to high, add prawns; cook until prawns are changed in colour. Remove mixture from pan.
4.Heat remaining oil in same pan; cook paste, stirring, until fragrant. Whisk in yogurt; cook over very low heat until warmed through. Return prawn mixture to pan; cook until heated through. Sprinkle with coriander leaves.