Soak the beans for 12 hours in cold water. Put them in a saucepan with cold water, season with salt, paprika, the bayleaf and nutmeg. Bring to the boil and simmer for 2 hours. Add the finely chopped onion, previously fried in butter and sprinkled with the flour. Stir into the soup and boil for 15 minutes longer. This soup may be either served as it is, or the beans can be rubbed through a sieve. Strips of toasted bread are served with it.