Preheat oven to 400°F (200°C).

Cut butternut squash in half lengthwise. Scoop out seeds. Drizzle with olive oil and roast cut-side up for 40-45 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 flesh of the roasted butternut squash and add it to the pot.

Pour in vegetable broth, cinnamon, and nutmeg. Bring to a boil, then reduce heat and simmer for 15 minutes.

Use an immersion blender or transfer to a regular blender and blend until smooth.

Season with salt and pepper to taste.