Bring a large pot of salted water to a boil. Add 8 ounces of penne pasta and cook according to package directions until al dente (usually about 10-12 minutes). Drain the pasta thoroughly and set aside.
Preheat your oven to 375°F (190°C). In a small bowl, toss 1/2 cup breadcrumbs with 1 tablespoon olive oil until evenly coated. This will give the topping a golden, crunchy texture when baked.
In a large mixing bowl, combine the cooked penne pasta, 2 cups shredded chicken, and 2 cups Alfredo sauce. Sprinkle in 1 teaspoon garlic powder, 1 teaspoon onion powder, 1/2 teaspoon salt, and 1/2 teaspoon black pepper. Stir everything gently but thoroughly to make sure the pasta and chicken are well coated with the sauce and seasonings.
Stir in 1 cup shredded mozzarella and 1 cup grated Parmesan cheese into the pasta mixture. The cheeses will melt during baking, adding creaminess and flavor throughout the casserole.
Grease your 9x13 inch baking dish lightly with oil or butter. Pour the pasta mixture into the dish, spreading it out evenly. Then sprinkle the breadcrumb mixture over the top in an even layer to create that irresistible crust.
Bake in the preheated oven for 25-30 minutes or until the top is golden brown and the casserole is bubbling around the edges. The cheese should be melted and gooey, and the breadcrumbs crisp and fragrant.
Remove from the oven and let it rest for 5 minutes before serving. Garnish with freshly chopped parsley for a pop of color and freshness. Serve warm and enjoy!