Bring a large pot of salted water to a boil. Cook the fettuccine pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the sliced andouille sausage and sauté for about 5 minutes, or until browned and cooked through.
Add the diced onion, garlic, and bell pepper to the skillet. Sauté for another 3-4 minutes until the vegetables have softened.
Stir in the shrimp, Cajun seasoning, and red pepper flakes. Cook for 3-4 minutes, or until the shrimp turn pink and opaque.
Pour in the heavy cream and chicken broth. Stir well to combine, allowing the sauce to simmer for about 5 minutes, or until it thickens slightly.
Add the cooked fettuccine to the skillet, tossing to coat the pasta in the creamy Cajun sauce. Stir in grated Parmesan cheese and season with salt and pepper to taste.
Remove from heat and let rest for a minute. Garnish with fresh parsley before serving.