Bring a large pot of salted water to a rolling boil. Cook the fettuccine according to package directions until al dente. Drain and set aside, reserving 1/2 cup pasta water.

Meanwhile, pat chicken breasts dry and season both sides with salt and black pepper.

In a large skillet over medium heat, melt 2 tablespoons butter. Add minced garlic and sauté about 1 minute until fragrant (don’t let it brown).

Add the chicken breasts to the skillet. Cook 5–7 minutes per side depending on thickness, until the internal temperature reaches 165°F (74°C) and the meat is no longer pink. Remove the chicken to a cutting board and let rest 5 minutes before slicing.

Lower heat to medium-low and add the heavy cream to the same skillet. Bring to a gentle simmer, scraping up any browned bits for flavor.

Stir in the remaining butter and grated Parmesan cheese a little at a time until the sauce becomes smooth and creamy. If the sauce seems too thick, whisk in a tablespoon or two of reserved pasta water. Season to taste.

Toss the cooked fettuccine directly into the sauce so every strand is coated. Slice the rested chicken and arrange on top. Finish with chopped parsley and a grind of black pepper.