Put water in a large pot on high heat.
Add chicken pieces. Bring to a boil. Turn down heat to a simmer.
Cook until chicken is done. About 20 minutes.
Remove chicken from the broth that has been created. Set aside too cool.
Pour broth into bowl and set aside.
Remove chicken flesh from the bones. Chop and set aside.
Pour the olive oil in the original pot. Place on medium heat.
Add onions, and garlic. Cook until soft.
Add fennel, carrots and celery.
Add 4 cups broth. Cook until the vegetables are soft.
Add additional 4 cups broth.
Using and immersion blender, blend all vegetables until a smooth soup emerges.
Add chopped chicken.
Heat and serve.