In a large heavy-duty pot, sauté onions and garlic in the butter until fragrant. Add celery and carrots and continue to cook until onions are translucent in color.
Add rosemary and thyme, cooking until herbs are fragrant and well blended.
Add broth, chicken, bay leaves, salt and pepper. Bring soup to a boil, then reduce to simmer and cook for 2 hours.
Notes
Freezer Option: This soup freezes well and is perfect to keep on hand through cold season. To reheat, allow to thaw and heat slowly on stovetop or in the microwave.