Heat the olive oil in a large deep skillet or Dutch oven over medium-high heat.
Add the chicken pieces to the skillet and season with salt, black pepper, and dried Italian seasoning. Cook for 5-6 minutes, stirring occasionally, until the chicken is browned and cooked through. Remove chicken from the skillet and set aside.
In the same skillet, add the minced garlic and sauté for 1 minute until fragrant, stirring constantly to avoid burning.
Pour in the chicken broth and whole milk, scraping the bottom of the skillet to release any browned bits.
Add the uncooked penne pasta to the skillet and stir to combine. Bring the mixture to a boil, then reduce heat to medium-low.
Cover and simmer for 12-15 minutes, stirring occasionally, until the pasta is tender and most of the liquid is absorbed.
Return the cooked chicken to the skillet and stir in the grated Parmesan cheese and unsalted butter until the cheese and butter are melted and the sauce is creamy.
Cook for an additional 2 minutes, stirring gently to combine all ingredients and heat through.
Remove from heat and sprinkle with chopped fresh parsley before serving.