Spray a large Dutch oven with olive oil. Add the onions and cook, stirring, until they are soft. Add the Canadian bacon, carrots, celery, and cook, stirring constantly for 2 minutes. Add remaining ingredients and simmer for 30 minutes. Put 1 cup of the soup in a food processor or blender and blend until smooth. Return to the pot to thicken the mixture.
Makes 8 servings