01 - Bring a large pot of salted water to a boil. Cook fettuccine according to package directions until al dente. Reserve 1/2 cup pasta water before draining.
02 - Pat chicken breasts dry with paper towels. Season both sides generously with salt and pepper.
03 - Heat olive oil in a large skillet over medium-high heat. Add chicken and cook 5-6 minutes per side until golden brown and internal temperature reaches 165°F. Remove to plate and rest 5 minutes before slicing thinly.
04 - Reduce skillet heat to medium. Add butter and minced garlic. Sauté 1 minute until fragrant, being careful not to burn garlic.
05 - Pour in heavy cream and bring to gentle simmer. Whisk in Parmesan cheese until completely melted and smooth. Stir in nutmeg if using. Season with salt and pepper to taste.
06 - Add cooked pasta to skillet and toss to coat evenly. Add reserved pasta water a tablespoon at a time if sauce is too thick.
07 - Gently fold sliced chicken into pasta. Serve immediately topped with fresh parsley and additional Parmesan cheese.