Cut the spaghetti squash in half lengthwise. Be careful as it is tough to cut through. Place the squash on towels if necessary to keep it in place.
Remove the seeds by scraping the inside of each half with a spoon.
Drizzle the inside of each half with the vegetable oil and sprinkle with salt and pepper.
Place the squash cut side down on a baking sheet. Roast in the oven until tender when pierced with a knife, approximately 30 minutes. Remove from oven and let cool slightly to handle.
While the squash is cooking, heat 1 Tablespoon of vegetable oil in a large nonstick skillet over medium high heat. Add the mushrooms and let cook until the mushrooms are beginning to soften and brown, approximately 5 minutes. Once you add them, do not touch them! This will help them brown.
Reduce skillet heat to low. Add the cream cheese, heavy cream, Parmesan cheese, garlic, dried sage, salt, and black pepper to the mushrooms. Stir to combine until melted.
Add the turkey and spinach to the mushroom mixture. Stir to combine, remove from heat, and set aside.
Reduce oven heat to 350F.
Fluff up the interior of each squash by using a fork and shredding at the squash flesh. This will make the "noodles"!
Add the mushroom turkey sauce mixture to each half of the squash and gently stir/fold to combine.
Sprinkle the mozzarella cheese across the top of each squash half.
Bake the squash until the cheese is melted, approximately 15 minutes. Put under the broiler at the end if desired for browned cheese, just make sure you do not have the squash on a silicone baking mat or parchment paper at this time. Serve immediately.