Season & Blacken Chicken: In a bowl, toss sliced chicken breast strips with 1 tablespoon of Cajun seasoning and 1/2 teaspoon salt. Heat 1 tablespoon olive oil in a deep 12-inch skillet over medium-high heat. Add chicken in a single layer and sear for 5 to 6 minutes, turning once, until nicely browned and cooked through. Transfer to a plate and set aside.
Sauté Veggies & Aromatics: In the same skillet, melt 1 tablespoon butter over medium heat. Add the sliced bell peppers, diced onion, and 1/2 teaspoon Cajun seasoning. Sauté for 3 to 4 minutes until peppers are slightly tender with caramelized edges. Add minced garlic and cook for 1 minute until fragrant.
Simmer One-Pot Pasta: Pour in 2 1/2 cups of chicken bone broth, 1 cup of heavy cream, and the uncooked penne pasta. Stir well, ensuring pasta is submerged. Bring to a rapid simmer, cover with a tight-fitting lid, turn heat to medium-low, and cook for 10 to 12 minutes, stirring every 2 to 3 minutes until pasta is tender al dente and sauce is thick.
Melt Cheese into Velvety Sauce: Uncover the skillet and reduce heat to low. Add the softened cream cheese and freshly grated Parmesan cheese. Stir continuously for 2 minutes until cheeses dissolve into a luxurious, glossy reddish-orange cream sauce.
Reincorporate Chicken & Serve: Return the cooked blackened chicken and any resting juices back to the skillet. Toss gently for 1 minute until everything is piping hot. Garnish with sliced green scallions and chopped fresh parsley. Serve immediately!