Cook the Pasta: Bring a large pot of generously salted water to a rolling boil. Add the penne pasta and cook for 10 to 12 minutes, or until al dente. Drain and set aside.

Sauté the Chicken: Heat olive oil in a large skillet over medium heat. Season chicken with Cajun seasoning and sauté for 4 to 5 minutes until golden brown and cooked through. Keep warm.

Cook the Shrimp: In the same skillet, add shrimp and cook for 2 to 3 minutes until pink and opaque. Remove and combine with chicken.

Sauté the Sausage and Veggies: Increase heat to medium-high and add sausage. Brown for 2 minutes, then add bell peppers, red onion, and garlic, cooking for 4 minutes.

Create the Sauce: Pour in heavy cream and simmer for 2 to 3 minutes. Stir in Parmesan cheese until melted. Adjust seasoning if needed.

Combine Everything: Return chicken and shrimp to the skillet with pasta. Toss to coat in the sauce and heat through for 1 to 2 minutes.

Add Garnish and Serve: Sprinkle parsley over the dish and serve warm.