Bring a large pot of salted water to a boil. Cook the fettuccine according to package directions until al dente. Reserve ½ cup of pasta water, then drain and set aside.
While the pasta cooks, heat olive oil in a large skillet over medium-high heat. Season the chicken with salt, pepper, and Italian seasoning. Sear the chicken slices for 3–4 minutes per side or until golden and cooked through. Transfer to a plate and keep warm.
In the same skillet, reduce heat to medium. Add the butter and minced garlic. Sauté for 1–2 minutes until fragrant, being careful not to brown the garlic.
Pour in the heavy cream and bring to a gentle simmer. Stir in the grated Parmesan cheese and cook for 3–4 minutes, stirring until the sauce is smooth and thickened slightly. If the sauce is too thick, stir in a splash of reserved pasta water.
Add the cooked fettuccine and seared chicken back into the skillet. Toss everything together until well coated in the Alfredo sauce.
Top with fresh parsley and extra Parmesan if desired. Serve immediately while hot and creamy.