1. Melt the butter or margarine in a large saucepan; add the onion and saut� gently for 5 minutes until soft. Add the cauliflower flowerets and potato slices. Cover and cook for 10 minutes.
2. Stir in the broth, bring to a boil, then cover and simmer for about 25 to 30 minutes or until all the vegetables are very soft.
3. Transfer to a blender and work until smooth. Return the pur�e to the rinsed-out saucepan and stir in the milk.
4. Heat the pur�e gently until simmering, then remove from heat and stir in the grated cheese. Season to taste with salt and pepper.
5. Pour the soup into individual soup bowls and swirl 1 tablespoon cream into each in a light feathery pattern over the entire surface of the soup. Place a quarter of the remaining cheese on each and sprinkle a little chopped parsley over the top.