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. Transfer to a plate, rest 5 minutes, then slice thinly.
04 - Reduce skillet heat to medium. Add butter and minced garlic. Sauté 1 minute until fragrant but not browned.
05 - Pour in heavy cream and bring to a 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 drained pasta to the skillet. Toss vigorously to coat evenly in sauce. Thin with reserved pasta water if needed for desired consistency.
07 - Add sliced chicken to pasta and toss gently. Serve immediately topped with fresh parsley and additional Parmesan cheese.