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 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 roasted squash and add it to the pot. Pour in vegetable broth, cinnamon, and nutmeg. Bring to a boil, then reduce heat and simmer for 10 minutes.

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

Season with salt and pepper to taste.