Preheat Oven: Preheat your oven to 400°F (200°C).
Prepare Spaghetti Squash: Cut the spaghetti squash in half lengthwise and scoop out the seeds. Drizzle the cut sides with 1 tablespoon of olive oil and sprinkle with a pinch of salt and pepper. Place the squash cut-side down on a baking sheet and roast for 40-50 minutes, or until tender.
Cook the Chicken: While the squash is roasting, heat the remaining tablespoon of olive oil in a large skillet over medium-high heat. Add the chicken pieces, season with Italian seasoning, salt, and black pepper, and cook for 6-8 minutes, or until fully cooked and golden brown. Remove the chicken and set aside.
Prepare the Sauce: In the same skillet, reduce the heat to medium. Add the minced garlic and sauté for 1 minute, or until fragrant. Pour in the heavy cream and stir in the Parmesan cheese. Add the red pepper flakes (if using). Simmer for 3-4 minutes, or until the sauce thickens slightly.
Combine Chicken and Sauce: Return the cooked chicken to the skillet and toss to coat in the creamy Parmesan sauce.
Scrape the Spaghetti Squash: Once the spaghetti squash is roasted and cool enough to handle, use a fork to scrape the flesh into spaghetti-like strands. Transfer the squash strands to the skillet with the chicken and sauce.
Toss and Serve: Toss everything together until well combined. Garnish with fresh parsley, if desired, and serve hot.