In a large pot, bring water to a boil and generously salt it. Add the penne pasta and cook according to package instructions, about 10-12 minutes, until al dente. Drain the pasta in a colander and set it aside.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Season the chicken breast with Cajun seasoning, then add it to the hot skillet. Cook for 4-5 minutes until golden brown and fully cooked, then remove and keep warm.

Using the same skillet, add the shrimp and cook until they turn pink and opaque, about 2-3 minutes. Set them aside with the chicken.

Add more olive oil if needed, then toss in the sliced andouille sausage. Sauté for 2 minutes, then add bell peppers, red onion, and garlic. Cook until the vegetables are tender, about 4 minutes.

Pour in the heavy cream and stir to combine. Let simmer for 2-3 minutes to thicken. Add the grated Parmesan cheese, stirring until it melts. Season with salt and pepper to taste.

Return the chicken and shrimp to the skillet, add the drained pasta, and toss gently with tongs or spatula until well coated in the creamy sauce. Allow the dish to meld for 1-2 minutes.

Sprinkle with chopped parsley and serve warm directly from the skillet.