Cook the pasta according to the package directions until al dente. Drain and set aside.
Melt the light butter in a large skillet over medium heat. Add the minced garlic and cook for about 30 seconds.
Sprinkle the flour over the garlic and butter and whisk for about 1 minute. Slowly whisk in the skim milk.
Cook for 3–5 minutes, stirring frequently, until the sauce begins to thicken.
Reduce the heat and stir in the softened light cream cheese until smooth. Add the Parmesan, Italian seasoning, onion powder, salt, and pepper.
Add the cooked pasta and shredded chicken to the skillet and stir until everything is coated in the creamy sauce.
Transfer the mixture to a greased 9×13-inch casserole dish. Sprinkle the reduced-fat mozzarella evenly over the top.
Bake at 375°F for 20–25 minutes, or until the casserole is hot and bubbly and the cheese has melted. Sprinkle with fresh parsley before serving.