Preheat oven to 450º F. 2. Cut squashes in half, remove the seeds and place cut side up in a large baking dish.  Drizzle with 1 tablespoon olive oil and season with salt and pepper, add 1/4 inch of water and cover with tinfoil.   Place in oven and bake for around 35-40 minutes, until tender, remove from heat and let cool. 3. Meanwhile, in a small pot, bring 2 cups water to a boil and then add quinoa. Reduce to a simmer and let cook for 15-20 minutes, or until quinoa has absorbed all water. Remove from heat. 4. In a large pan, heat remaining olive oil and sauté mushrooms and onions on medium heat until softened. Add in the garlic after a few minutes, then add the chopped walnuts if using. Cook until fragrant and onions are translucent.  Season with salt and pepper to taste. 5. After squash has cooled, scoop out the insides, leaving about a 1/4 inch of flesh, being careful not to scoop out the bottom.  In a large bowl, combine quinoa, butternut squash, mushrooms, onions and garlic,  salt and pepper to taste. Mix well. 6.  Turn oven down to 375º F. Spoon mixture back into the hollow butternut squashes and return them to the oven for 20-25 minutes, or until top is golden brown. Serve with a garnish of basil.