Heat half the oil a large saucepan over medium-high heat. Cook lamb, stirring, for 5 minutes or until browned. Transfer to a plate. Heat remaining oil in pan. Cook onion, stirring, for 3 minutes or until softened.
Add curry paste and cook, stirring, for 1 minute. Return lamb to pan with stock, tomatoes and vinegar and bring to the boil. Reduce heat and simmer, covered, for 1 hour.
Add pumpkin and simmer, uncovered, for 20 minutes. Add beans and simmer, uncovered, for 5-7 minutes or until lamb and pumpkin are tender.
Stir in half the coriander. Serve curry topped with yoghurt and remaining coriander.