Bring a large pot of salted water to a rolling boil. Add the penne pasta and cook until al dente, about 10-12 minutes. Reserve 1 cup of pasta water, then drain pasta and set aside.

In a large skillet, heat olive oil over medium-high heat. Season chicken with Cajun seasoning, sear for 4-5 minutes on each side until cooked through. Remove chicken and let rest before slicing.

In the same skillet, add more olive oil if necessary, then add shrimp. Cook shrimp for 2-3 minutes until pink and opaque. Remove and set aside with chicken.

Add sliced andouille sausage to the skillet, sauté for 2 minutes, then add bell peppers, onion, and garlic. Cook for an additional 4 minutes until veggies are tender.

Reduce heat to medium and add heavy cream, stirring to mix with veggies. Let simmer 2-3 minutes to thicken. Gradually add Parmesan while stirring. Season with salt and pepper.

Add chicken and shrimp back to skillet along with drained pasta. Toss gently to coat in sauce and heat through for 1-2 minutes. Add reserved pasta water if sauce is too thick.

Garnish with chopped parsley and serve immediately, either plated or family-style.