Heat oven to 400°F (200°C). Grease a 9x13 baking dish with olive oil or butter.
Scatter the uncooked pasta evenly in the dish.
Top with the raw chicken pieces. Season with salt, pepper, and Italian seasoning.
In a bowl, whisk together chicken broth, heavy cream, minced garlic, and cream cheese until mostly smooth. Some little bits of cream cheese are fine; they melt in the oven.
Stir in 1 cup Parmesan.
Pour the sauce over the pasta and chicken. Press down to ensure the pasta sits in liquid. Cover the dish tightly with foil.
Bake for 30 minutes covered. This steams the pasta and gently cooks the chicken.
Remove foil, stir well, and check liquid. If pasta looks dry, add 1/4 to 1/2 cup hot water or broth.
Top with mozzarella if using. Bake 10–15 minutes uncovered until the pasta is al dente, sauce is creamy, and the top is lightly golden.
Let it rest 5 minutes. The sauce thickens as it stands.
Sprinkle with fresh parsley and extra Parmesan. Taste and adjust salt and pepper.
Use short, tubular pasta. It cooks evenly and holds creamy sauce well.
Grate your own Parmesan. Pre-grated can clump. Freshly grated melts smoothly.
Check at the 30-minute mark. Every oven runs different. Add a splash of hot liquid if needed.
Cut chicken evenly. Uniform 1-inch pieces cook through right as pasta finishes.
