Cook the onion, celery, and garlic over high heat for 2 minutes, stirring constantly until they begin to colour. Add all remaining ingredients. Cover the pot and simmer gently for 30 minutes. Ladle into warm soup bowls and serve piping hot.
A tablespoon of blond "roux" mixed with some of the stock and stirred into the soup a few minutes before the simmering is complete adds a silky texture to the dish.