Add the celery, onion, garlic, and celery salt and pepper to taste.
Add the bay leaf and cook the mixture until the celery and onion are tender, about 20 minutes, stirring often.
Add the potatoes celery root, and chicken stock. Bring to a boil then reduce heat a simmer and continue simmering, partially covered, for 20 minutes.
Puree using an immersion blender. If you do not have an immersion blender you can use a regular blender, working in batches, but let the soup cool some first or it will explode in the blender.
Stir in the cream and keep over heat until warmed through.