Heat the butter or margarine in a large, heavy pan and add the sliced vegetables with a little salt and pepper. Stir well, cover and simmer for about 10 minutes, or until the vegetables are softened and slightly golden in color.
Add the stock and simmer for 15 - 20 minutes, or until the soup has thickened and the vegetables are very tender.
Strain the soup reserving the liquid. Put the vegetables into a blender and blend until smooth or just slightly chunky, then return to the liquid. Mix well. Or use a hand blender to blend the vegetables right in the cooking pot.
Add the grated cheese and stir. Reheat, stirring constantly, until the soup is thick and creamy. Taste for seasoning and add salt and pepper if needed.