In a large pot sauté onion in butter on medium heat until golden. Add the leek, celery, carrots, garlic and continue to cook for a further 4 to 5 minutes or until vegetables are just golden.
Add remaining ingredients, except cream, cardamom, limejuice and coriander and bring to a boil. Cover and reduce heat to low. Simmer the soup for 30 minutes or until cauliflower is tender. Add the cream, cardamom and limejuice. Remove lid and continue to simmer for a further 15 minutes. Adjust seasoning.
Sprinkle with chopped coriander and serve.