Preheat the oven to 400°F (or 425°F if using the widthwise method). Cut the spaghetti squash in half lengthwise and scoop out the seeds. Brush the insides with olive oil and sprinkle with salt and pepper. Place the squash cut-side down on a parchment-lined baking sheet and roast for 40-45 minutes, or until fork-tender.

While the squash is roasting, heat olive oil in a skillet over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes. Then add the minced garlic and sliced mushrooms, cooking until the mushrooms release their liquid and brown, approximately 8-10 minutes.

Stir in the dried sage and continue to sauté for another minute. Then, add the creamer and cream cheese to the skillet, stirring to combine until the cream cheese melts and the sauce thickens. Pour in the broth and season with salt, pepper, and a pinch of nutmeg. Let the sauce simmer on low heat.

Once the spaghetti squash is done cooking, remove it from the oven and use a fork to fluff up the strands. Transfer the squash strands to the skillet with the mushroom sauce, stirring gently to combine all ingredients thoroughly.

Serve the spaghetti squash in its shell or in a large bowl, topped with vegan parmesan or crumbled feta cheese and fresh parsley for garnish. Optionally, drizzle with truffle oil and sprinkle with toasted pine nuts for an extra flavor punch.