01 - Preheat the oven to 400°F. Grease a 9x13-inch baking dish thoroughly.
02 - Boil salted water in a large pot and cook pasta until just al dente. Drain and set aside.
03 - Heat olive oil in a large skillet over medium-high heat. Add diced chicken, season with salt and pepper, and cook 6-7 minutes until browned and fully cooked. Remove from heat.
04 - In the same skillet, melt butter over medium heat. Add minced garlic and sauté until fragrant, about 1 minute. Pour in heavy cream and bring to a gentle simmer. Stir in Parmesan, mozzarella, Italian seasoning, nutmeg if using, and season to taste. Cook 2-3 minutes until sauce thickens slightly.
05 - In a large mixing bowl, combine cooked pasta, chicken, and Alfredo sauce. Toss well to coat evenly.
06 - Transfer the pasta mixture to the prepared baking dish. Evenly sprinkle remaining shredded mozzarella cheese on top.
07 - Bake uncovered for 20-25 minutes until the topping is golden and bubbling.
08 - Allow to rest for 5 minutes. Garnish with chopped fresh parsley before serving.