Step 1: In a large pot, bring salted water to a rolling boil.
Step 2: Add the fettuccine and cook according to package instructions until al dente. Reserve 1/2 cup of the starchy pasta water, then drain the pasta and set aside.
Step 3: While the pasta is cooking, season the chicken breasts generously with salt and freshly ground black pepper on both sides.
Step 4: In a large skillet, heat the olive oil over medium-high heat. Add the seasoned chicken breasts and cook for 6-7 minutes per side, or until they are cooked through and beautifully golden brown. If using minced garlic, add it during the last minute of cooking. Remove the chicken from the skillet and let it rest for a few minutes before slicing.
Step 5: In the same skillet (no need to clean it!), reduce the heat to medium. Add the unsalted butter and allow it to melt completely.
Step 6: Pour in the heavy cream and stir well to combine with the melted butter. Let the mixture simmer gently for about 3-4 minutes, stirring occasionally, until it begins to slightly thicken.
Step 7: Gradually whisk in the freshly grated Parmesan cheese until it is fully melted and the sauce is smooth and creamy. If the sauce becomes too thick, slowly add the reserved pasta water, a tablespoon at a time, until your desired consistency is reached. Season with the optional nutmeg, and adjust salt and pepper to taste.
Step 8: Add the drained fettuccine pasta directly into the Alfredo sauce. Toss the pasta gently until every strand is evenly coated in the rich, creamy sauce.
Step 9: Slice the rested cooked chicken breasts into desired pieces (strips or cubes) and arrange them artfully on top of the coated pasta.
Step 10: Garnish generously with fresh chopped parsley and an extra sprinkle of Parmesan cheese, if desired. Serve immediately and enjoy your homemade Chicken Fettuccine Alfredo!