Season the chicken breasts with Cajun seasoning, salt, and pepper. Heat olive oil in a large skillet over medium heat. Add the chicken and cook for about 6-7 minutes on each side, or until cooked through and no longer pink in the center. Remove from the skillet and let rest for a few minutes before slicing.

In a large pot, bring salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Reserve ½ cup of pasta water, then drain the pasta.

In the same skillet used for the chicken, melt the butter over medium heat. Add minced garlic and sauté for about 1 minute until fragrant.

Pour in the heavy cream and bring to a simmer. Stir in the grated Parmesan cheese until melted and smooth. If the sauce is too thick, add a little reserved pasta water to reach desired consistency.

Add the cooked fettuccine to the sauce and toss to coat. Slice the chicken and place it on top of the pasta. Garnish with chopped parsley before serving.