Bring a large pot of salted water to a boil. Add the penne pasta and cook according to package directions until al dente. Drain and set aside.

While the pasta cooks, pat the chicken breasts dry with paper towels. Slice them into thin strips or bite-sized pieces for quicker cooking.

In a bowl, season the chicken pieces with Cajun seasoning, salt, and black pepper. Toss until the chicken is evenly coated.

Heat the olive oil in a large skillet over medium-high heat. Add the seasoned chicken in a single layer and cook for 5–7 minutes, stirring occasionally, until the chicken is browned and cooked through. Transfer the cooked chicken to a plate and set aside.

In the same skillet, reduce the heat to medium and add the unsalted butter. Once melted, add the minced garlic and cook for about 30 seconds, stirring frequently, until fragrant but not browned.

Pour in the chicken broth and use a wooden spoon to gently scrape up any browned bits from the bottom of the skillet. Let the mixture simmer for 2–3 minutes to reduce slightly.

Stir in the heavy cream, paprika, and red pepper flakes if using. Bring the sauce to a gentle simmer and cook for 3–4 minutes, stirring occasionally, until it starts to thicken.

Lower the heat and gradually add the grated Parmesan cheese, stirring constantly until it melts and the sauce becomes smooth and creamy.

Add the cooked penne pasta and the cooked chicken back into the skillet. Toss everything together until the pasta and chicken are well coated in the creamy Cajun sauce.

Sprinkle the chopped fresh parsley over the pasta. Taste and adjust seasoning with a little extra salt or black pepper if needed before serving warm.