1. Bring a large pot of salted water to a boil and cook the penne until al dente. Drain and set aside.

2. Toss the chicken pieces with Cajun seasoning, salt, and black pepper until evenly coated.

3. Heat olive oil in a large skillet over medium-high heat.

4. Add the chicken and cook for 5 to 7 minutes, turning occasionally, until golden and cooked through. Transfer the chicken to a plate.

5. Reduce the heat to medium and melt the butter in the same skillet.

6. Add the onion and red bell pepper, then cook for 3 to 4 minutes until softened.

7. Stir in the garlic and cook for 30 seconds, just until fragrant.

8. Pour in the chicken broth and heavy cream, stirring well and scraping up any browned bits from the bottom of the skillet.

9. Add the Parmesan cheese and stir until the sauce is smooth and creamy.

10. Return the cooked pasta to the skillet and toss until coated in the sauce.

11. Add the cooked chicken back to the skillet and stir everything together.

12. Sprinkle in the mozzarella cheese and let it melt into the pasta.

13. Garnish with chopped parsley and serve hot.