This soup is popular in the United States

In a large casserole, put all ingredients except Cayenne pepper, salt and butter.
Bring to boil, reduce heat and simmer 45 Minutes until vegetables are tender.
Purée the soup with a blender or a food processor.
Strain soup with a sieve or china cap, pour back into casserole and season to taste with salt and Cayenne pepper. Simmer 5 Minutes add butter and stir until melted.