Cook the Pasta: Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Drain and set aside, reserving a cup of pasta water.
Season the Shrimp: In a bowl, toss the shrimp with Cajun seasoning until evenly coated.
Sauté the Shrimp: In a large skillet, heat olive oil over medium-high heat. Add the seasoned shrimp and cook for 2-3 minutes on each side, until pink and opaque. Remove shrimp from the skillet and set aside.
Create the Sauce: In the same skillet, reduce the heat to medium and add butter. Once melted, add minced garlic and sauté for about 1 minute until fragrant.
Add Cream and Cheese: Slowly pour in the heavy cream, stirring constantly. Allow the cream to simmer for 2-3 minutes, then gradually whisk in the grated Parmesan cheese. Stir until the cheese has melted and the sauce is smooth.
Combine: Return the cooked shrimp to the skillet. Add the cooked fettuccine and toss everything together, adding reserved pasta water little by little until you reach your desired sauce consistency.
Season and Serve: Season with salt and pepper to taste. Serve immediately, garnished with chopped parsley.