Heat oil in a large pot set over medium-high heat. Add squash, leeks and carrot. Sauté over medium heat for 10 minutes.
Add apple, thyme and ground celery seed. Add broth and cider. Bring mixture to a boil.
Reduce heat to medium-low, cover pot and simmer for 30 minutes. Let mixture cool slightly.
Using an immersion blender, purée soup until smooth.
Add more chicken broth, if desired, to thin the soup until it reaches your desired consistency. Season with salt and pepper. Bring soup to a simmer and serve hot. Garnish with cooked, crumbled bacon.