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.

Drizzle squash with olive oil and roast for 40-50 minutes, or until tender.

While squash is roasting, sauté onion in a large pot until softened.

Once squash is cool enough to handle, scoop out the flesh and add it to the pot with the onion.

Add vegetable broth, nutmeg, and cinnamon to the pot. Bring to a simmer and cook for 10 minutes.

Using an immersion blender, blend the soup until smooth. If desired, stir in heavy cream.

Season with salt and pepper to taste.

Serve hot, garnished with pepitas and a dollop of crème fraîche.