01 - Cook fettuccine in a large pot of salted boiling water according to package directions until al dente. Reserve 1/2 cup pasta water, then drain and set aside.
02 - Season sliced chicken breasts evenly with salt and black pepper.
03 - Heat olive oil in a large skillet over medium-high heat. Add chicken and cook 4 to 5 minutes per side until golden brown and cooked through. Remove chicken from skillet and set aside.
04 - Reduce skillet heat to medium. Melt butter, then add minced garlic and sauté for 1 minute until fragrant.
05 - Pour in heavy cream and bring to a gentle simmer, stirring frequently. Reduce heat to low.
06 - Whisk in Parmesan cheese until the sauce is smooth and creamy. Season with salt, pepper, and optional nutmeg. Add reserved pasta water in small amounts if sauce becomes too thick.
07 - Return cooked chicken to skillet. Add drained fettuccine and toss until pasta is fully coated and chicken is evenly distributed.
08 - Serve immediately, topped with chopped fresh parsley and additional Parmesan cheese if desired.