Wash and peel the sweet potatoes and then cut them into small chunks.
In a soup pot, saute the onions, carrots and celery in oil until slightly soft.
Add the sweet potatoes, bay leaf and 8 cups of liquid (broth or broth/water combination) and bring to boil. Lower the heat to simmer and cover. Cook 10-15 minutes until the sweet potatoes are soft.
Remove the bay leaf and reserve. Use an emulsion blender to puree the mixture into a chunky soup: smooth sweet potatoes with celery chunks and carrot shreds.
Peel and shred the apples. Add to the pot and mix well.
Add the seasonings, including the bay leaf. Mix well and simmer 15 minutes or more, to allow the flavors to blend.
Ladle into bowls, top with diced apples, shredded carrot or cheese.