Melt butter in a large saucepan over medium heat. Add onion, carrot, celery and garlic. Season with salt and pepper stirring occasionally until vegetables are tender, about 20 minutes.
Add chicken stock, chestnuts, bay leaves and about 1 teaspoon salt. Simmer over medium - low heat until chestnuts are tender, about 45 minutes. Remove from heat and discard bay leaves.
Puree soup using immersion blender, or ben with a regular blender. Taste and adjust seasonings, if needed. Enjoy!