Bring a large pot of generously salted water to a boil and cook the fettuccine according to the package directions until al dente. Drain and set aside.

Season the chicken breasts evenly with Italian seasoning, kosher salt, and black pepper. In a large nonstick skillet over medium-high heat, warm the olive oil until shimmering. Sear the chicken undisturbed until deeply golden, approximately 4 to 6 minutes on each side. Add the butter to the pan and continue cooking, turning occasionally, until the chicken reaches an internal temperature of 165°F, roughly 16 minutes total. Remove from heat.

Transfer the cooked chicken to a cutting board, rest for 3 minutes, then slice into ½-inch-thick strips. Cover loosely with foil to retain warmth.

Wipe the skillet clean and return it to medium heat. Add the butter and once nearly melted, stir in minced garlic, garlic powder, nutmeg, kosher salt, and freshly cracked pepper. Sauté for about 1 minute until aromatic.

Raise the heat to medium-high and gradually incorporate the heavy cream. Allow the mixture to come to a gentle simmer, then blend in the grated Parmesan. Stir continuously until the cheese is fully integrated, around 2 minutes. Lower the heat to medium-low and continue stirring until the sauce thickens, about 5 minutes more. Fold in the cooked pasta, ensuring it is thoroughly coated.

Plate the pasta into serving bowls and top with the sliced chicken. Garnish with freshly chopped parsley and additional cracked pepper as desired.