01 - Preheat your oven to 200°C (400°F). Lightly grease a 23x33 cm (9x13 inch) baking dish.
02 - Cook the pasta in a large pot of salted boiling water according to package directions until al dente. Drain thoroughly and set aside.
03 - In a large skillet, heat the olive oil over medium-high heat. Season the diced chicken with salt and pepper. Add the chicken to the hot skillet and cook for 5-7 minutes, until it is golden brown and cooked through. Remove the chicken from the skillet and set aside.
04 - In the same skillet, melt the butter over medium heat. Add the minced garlic and sauté until fragrant, about 1 minute. Stir in the flour and cook for an additional minute.
05 - Gradually whisk in the milk and heavy cream, bringing the mixture to a gentle simmer. Cook, stirring constantly, for 3-4 minutes or until the sauce has thickened.
06 - Remove the skillet from the heat. Stir in the grated Parmesan cheese, nutmeg, and salt and pepper to taste until the sauce is smooth and well combined.
07 - In a large bowl, combine the cooked pasta, seared chicken, and the prepared Alfredo sauce. Toss gently to ensure all components are evenly coated.
08 - Transfer the pasta and chicken mixture to the prepared baking dish. Evenly distribute the shredded mozzarella cheese and the additional grated Parmesan cheese over the top.
09 - Place the dish in the preheated oven and bake for 20 minutes, or until the cheese is melted and bubbly.
10 - Garnish with fresh chopped parsley, if desired. Serve this comforting bake hot.