Cut the butternut squash in half lengthwise and remove the seeds and stringy pulp. Put the halves flesh side down in a baking dish, add 1 cup of water. Wrap the sweet potato in aluminum foil. Bake the squash and sweet potato for 30 minutes until you can pierce through the skin easily.
While the squash is roasting, heat olive oil in a skillet over medium heat. Cook leeks until softened, about 5 minutes. Add garlic and spices, stir and cook for another minute. Add wine and cook for another two minutes to meld the flavors. Set aside.
Remove the squash and sweet potato from the oven. When the squash to cool enough to handle, scrape the flesh from the skin. Cut the sweet potato into half, no need to peel - it will be totally pureed and you'll retain all the nutrients in the skin.
Add the squash, sweet potato, leek-spice mixture, and almond milk to your blender. Process on Puree (or until smooth, if you're not using the Ninja one-touch). Place in a saucepan to heat, stir in butter to add a touch of richness, if desired.
The butter is optional, but adds to the velvet texture of the finished soup.