Cook the pasta. Bring a large pot of salted water to a boil. Cook fettuccine until just shy of al dente. Reserve 1 cup of pasta water, then drain and set aside.

Prep the chicken. Pat the chicken dry, then season both sides with salt and pepper. For quicker cooking and more browning, slice breasts horizontally into cutlets.

Sear the chicken. Heat olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add chicken and cook 3–4 minutes per side, until golden and cooked through. Transfer to a plate and rest; slice into strips once cooled slightly.

Sauté the garlic. Lower the heat to medium. Add remaining 3 tablespoons butter to the same skillet. Stir in minced garlic and cook 30–45 seconds until fragrant, not browned.

Build the sauce base. Pour in heavy cream and a pinch of salt and pepper. Simmer gently for 3–4 minutes, stirring. Keep the heat medium to avoid boiling.

Melt in the cheese. Reduce heat to low. Add Parmesan in small handfuls, stirring until smooth. If the sauce seems too thick, whisk in splashes of reserved pasta water. Add a tiny pinch of nutmeg.

Add pasta and chicken. Toss in the cooked pasta and sliced chicken. Use tongs to coat everything. Add more pasta water as needed to get a silky, glossy sauce that clings.

Adjust and brighten. Taste and add more salt and pepper if needed. A small squeeze of lemon can brighten the richness—just a little.

Serve. Top with extra Parmesan and chopped parsley. Serve immediately while the sauce is at its creamiest.