Step 1: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Step 2: Slice the spaghetti squash in half lengthwise and scoop out the seeds. Brush the cut sides with olive oil and sprinkle with a pinch of salt.
Step 3: Place the squash halves cut-side down on the baking sheet and roast for 40 minutes until the skin is easily pierced with a fork.
Step 4: While the squash is roasting, melt butter in a medium saucepan over medium heat. Add garlic and sauté for 1 minute until fragrant.
Step 5: Pour in the heavy cream and bring to a gentle simmer. Cook for 3-5 minutes until the liquid reduces slightly.
Step 6: Remove from heat and stir in the Parmesan cheese until melted and smooth. Season with salt and pepper.
Step 7: Once the squash is cooked and cool enough to handle, use a fork to scrape the flesh into strands and place them in a large bowl. Drain any excess moisture.
Step 8: Add the cooked chicken and the prepared Alfredo sauce to the bowl with the squash strands. Toss well to combine.
Step 9: Transfer the mixture into a 9x13 inch baking dish. Top with shredded mozzarella cheese.
Step 10: Bake at 375°F (190°C) for 20 minutes until the cheese is golden and bubbly. Garnish with fresh parsley before serving.