celery, onion, leek and garlic in large saucepan. Add water, chicken
stock, salt and pepper and bring to a boil. Turn down heat, cover and
simmer 10 minutes. Add spinach, lettuce and watercress, cover again and
continue simmering 15 minutes. Whirl in blender, a little at a time,
until smooth. Return to saucepan. Stir in milk. Heat to boiling point.
Serve very hot topped with Croutons.