Preheat oven to 400°F (200°C).

Cut butternut squash in half lengthwise and scoop out seeds. Place cut-side up on a baking sheet and roast for 30-40 minutes, or until tender.

While squash is roasting, heat olive oil in a large pot over medium heat. Add onion and cook until softened, about 5 minutes. Add garlic and cook for 1 minute more.

Scoop out the roasted butternut squash flesh and add it to the pot. Add vegetable broth, sage, salt, and pepper. Bring to a simmer and cook for 10 minutes.

Using an immersion blender or a regular blender (carefully!), blend the soup until smooth.

Stir in the shredded chicken and heat through.

Serve hot.