In saucepan, cook onion carrot, salt and pepper to taste in butter over moderate heat. Add 1 tbsp of flour
Stir until the onion is soft.
Add broccoli, broth and water. Simmer the mixture, covered for 15 minutes or until broccoli is tender.
In a blender, puree the mixture in batches, transferring it as it is pureed to another heavy saucepan.
Place over moderate heat, quickly whisk in the sour cream and serve immediately.
Serves 4.
Tip: Add spinach leaves when you puree the soup to enhance the green colour.