Method

1. Melt the butter in a pot and add the onion and potatoes. Cook gently for about 10 minutes, stirring occasionally, without browning.
2. Add the stock and seasoning. Bring to the boil, then reduce the heat, cover and simmer gently for 20-25 minutes until the vegetables are very soft.
3. Either pass through a sieve or tip into a food processor / blender and purée until smooth. Return the soup to the pot and stir in the milk, broccoli, nutmeg and parsley. Bring to the boil, reduce the heat and simmer gently for 5- 10 minutes.
4. Stir the yogurt in just before serving.
5. Using a serrated knife cut a hollow into the bread rolls.  Place each roll into a soup plate.  Pour the hot soup into the roll.  Top with grated cheese and serve immediately.