Heat the oil in a large saucepan and add the onion. Cook for 3-4 minutes, until softened, then add the carrots, parsnip, potato, rice and lamb and cook for one minute.
Stir in the curry paste, then add the stock and mix well. Season with salt and freshly ground black pepper.
Bring to the boil, then reduce the heat, cover and simmer for 30 minutes, or until the vegetables are tender.
Pulse a hand blender in the soup a couple of times to purée it slightly, then stir in the coriander.
Ladle the soup into warm bowls and garnish with a few coriander leaves.
Serve with warm naan bread.