In a large skillet over medium heat, cook diced chicken breasts with Italian seasoning, salt, and pepper until browned and almost cooked through.
Stir in minced garlic and cook for 1 minute until fragrant.
Add marinara sauce, uncooked penne pasta, and chicken broth. Stir to combine and bring to a boil.
Reduce heat to a simmer, cover, and cook for 12-14 minutes, stirring occasionally, until pasta is tender and most of the liquid is absorbed.
Stir in shredded mozzarella and grated Parmesan cheese until melted and creamy.
Garnish with chopped fresh parsley and serve immediately.