Preheat oven to 400°F (200°C). Cut butternut squash in half, scoop out seeds, and place cut-side up on a baking sheet. Roast for 45-60 minutes, or until tender.

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

Once squash is cool enough to handle, scoop out the flesh and add it to the pot with the onion mixture. Add vegetable broth and maple syrup. Bring to a simmer and cook for 10 minutes.

Using an immersion blender or a regular blender, blend the soup until smooth. Season with salt and pepper to taste.