Preheat your oven to 350°F (175°C). Lightly grease a 2-quart or 9x9-inch baking dish. Cook the pasta according to package directions, but for 2-3 minutes less than the recommended time so it's al dente. Drain and set aside.
While the pasta cooks, melt the butter in a large skillet or Dutch oven over medium-high heat. Add the chicken cubes and cook until browned and the internal temperature reaches 165°F (74°C) on a digital thermometer. Remove the chicken from the skillet and set aside.
Reduce the heat to medium. Add the chopped onion and bell pepper to the same skillet and cook until softened, about 3-4 minutes. Add the minced garlic and cook for another minute until fragrant.
Pour in the cream of chicken soup, milk, and chicken stock. Whisk until the mixture is smooth.
Add the cubed cream cheese and stir continuously until it has completely melted into the sauce.
Stir in the dry Italian dressing mix and 2 tablespoons of the grated Parmesan cheese until well combined.
Return the cooked chicken to the skillet, then add the drained pasta. Stir everything together until the chicken and pasta are fully coated in the sauce.
Transfer the mixture to your prepared baking dish and spread it into an even layer. Sprinkle the remaining 1 tablespoon of Parmesan cheese over the top.
Bake for 30-40 minutes, or until the sauce is bubbling and the top is lightly golden brown. Let it rest for a few minutes before serving.