Preheat your oven to 375°F (190°C). Grease a large baking dish (9x13-inch) and set aside.
Bring a large pot of salted water to a boil. Cook the pasta according to the package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil (or butter) over medium heat. Add the minced garlic and cook for about 1 minute until fragrant. Stir in the flour and cook for another minute to form a roux. Gradually whisk in the chicken broth, followed by the heavy cream. Stir constantly until the mixture thickens (about 3-5 minutes).
Stir in the Parmesan cheese, 1 cup of mozzarella cheese, Italian seasoning, crushed red pepper flakes (if using), salt, and pepper. Continue to stir until the cheese has melted and the sauce is smooth and creamy.
Add the cooked pasta and the shredded/cubed chicken to the skillet with the sauce. Stir to coat everything evenly in the creamy garlic-Parmesan sauce.
Transfer the pasta mixture to the prepared baking dish. Sprinkle the remaining ½ cup of mozzarella cheese evenly over the top. Bake for 20-25 minutes, or until the cheese is melted and bubbly and the top is golden brown.
Garnish with fresh parsley or basil if desired. Serve hot and enjoy!
