Preheat the oven to 400°F and spray a large baking pan with non stick spray. Peel the butternut squash using a potato peeler. Cut off the ends and cut the squash in half long ways. Scoop out the seeds then cut the squash into chunks. Add to the prepared baking pan, toss with a 2 tablespoons of olive oil and salt and pepper then roast in the preheated oven for 40 minutes.
While it's roasting, heat the other 2 tablespoons of olive oil in a large dutch oven or stock pot and add the chopped onion over medium heat. Cook until the onion is translucent and starts to turn golden, 2-3 minutes.
When the squash is done, add it to the pot with the onions. Add the stock, stir and let simmer for 10 minutes at medium-high heat.
Using an immersion blender, mix the soup until it's a smooth and creamy consistency. Or transfer to a blender and mix well if you don't have an immersion blender.
Place back in the soup and add the maple syrup, nutmeg and cinnamon. Stir well.
Serve immediately or store in an air tight container in the fridge for up to three days.