Preheat oven to 350°F (175°C) and grease a 9×13-inch baking dish.
Cook egg noodles according to package directions until al dente. Drain and set aside.
In a skillet, melt butter over medium heat. Sauté onion and garlic until fragrant, about 2–3 minutes.
In a large bowl, combine cream of chicken soup, sour cream, milk, parsley, pepper, and half of the mozzarella cheese.
Add cooked noodles, shredded chicken, and sautéed onions to the bowl. Stir until everything is coated in the creamy sauce.
Transfer mixture to the prepared baking dish. Sprinkle remaining mozzarella and breadcrumbs evenly on top.
Bake for 25–30 minutes or until bubbly and golden brown on top.
Let rest for 5 minutes before serving.