Cook the pasta according to package instructions.
Season the steak strips with salt, pepper, and half of the Cajun seasoning.
In a large skillet, melt 2 tablespoons of butter over medium-high heat and add the steak.
Cook the steak for 3-4 minutes until browned, then remove from skillet and set aside.
In the same skillet, add the remaining butter and then the shrimp, seasoning with the rest of the Cajun seasoning.
Add minced garlic and cook for 1 minute, then pour in the heavy cream.
Stir in the Parmesan cheese until melted and the sauce thickens slightly.
Return the steak to the skillet and toss to combine with the shrimp and sauce.
Combine the cooked fettuccine with the sauce, tossing gently to coat.
Adjust seasoning with salt and pepper; serve garnished with parsley.