Cook the fettuccine according to package instructions in a large pot of salted boiling water. Drain and set aside, reserving 1/2 cup of pasta water.

While the pasta cooks, prepare the chicken. Pat the chicken breasts dry with paper towels. Rub with olive oil, garlic powder, onion powder, salt, and pepper.

Preheat a grill or grill pan over medium-high heat. Add the seasoned chicken breasts and cook for 6-7 minutes on each side, or until the internal temperature reaches 165°F (75°C). Remove from the grill and let rest for 5 minutes before slicing into strips.

In a large saucepan, melt the butter over medium heat. Add the heavy cream and bring to a simmer, stirring frequently. Cook for about 2-3 minutes until slightly thickened.

Stir in the grated Parmesan cheese until melted and smooth. If desired, add nutmeg for extra flavor. If the sauce is too thick, slowly add some reserved pasta water until you reach your desired consistency.

Add the cooked fettuccine to the sauce, tossing to coat the pasta evenly. Incorporate the grilled chicken slices on top and gently mix.

Serve immediately, garnishing with freshly chopped parsley.