In a large pot add the chicken broth, butternut squash, onion, carrot, celery, salt and minced garlic.
Bring to a boil, then reduce the heat to low. Cover and simmer for 25-30 minutes, or until the squash and vegetables are tender.
Use an immersion blender to puree the soup directly in the pot until smooth. Alternatively, carefully transfer the mixture to a blender in batches and blend until smooth.
Stir in the butter and garnish with heavy cream if desired.