Bring a large pot of water to a boil. Once boiling, add 1 tablespoon of salt. Add the fettuccine pasta and cook, stirring occasionally, until it is al dente, following the shortest cooking time on the package. Before draining, reserve 1 cup of pasta water. Then drain the pasta without rinsing.
Cut chicken breasts in half widthwise to make four thinner filets. Use a meat mallet or similar implement to give each piece a quick pound. Don't flatten chicken; we just want all the pieces fairly even in width. Season both sides with 1/4 teaspoon of salt and pepper and 1/2 teaspoon garlic powder and Italian seasoning.
Add olive oil to a large pot or pan that can hold all the pasta and heat it over medium heat. Once the oil is hot, add the seasoned chicken pieces in a single layer. Cook for about 3–4 minutes, then flip the chicken and add 1 tablespoon of butter to the pan. Cook for another 3–4 minutes, or until the chicken is cooked through, the juices run clear, and it reaches an internal temperature of 160°F. Remove the chicken to a plate, cover it loosely with foil, and let it rest for about 5 minutes before thinly slicing or dicing.
Cut the remaining butter into tablespoon pieces. Without wiping it out, place the butter in the same pot you cooked the chicken in and melt butter over medium-high heat. Once melted, add in onion and garlic and stir, scraping up browned bits leftover from the chicken. Sauté until tender, about 3 minutes. Pour in the cream plus 1/4 teaspoon salt and 1/4 teaspoon pepper. As soon as mixture boils, turn heat down to medium low. Simmer until thickened, about 1-3 minutes (see note 3).
Once thickened, remove pan from heat. Stir in the finely gratedcheese until melted and sauce is mostly smooth. Dump the drained pasta right on top of the sauce, along with 1/2 cup of the reserved pasta water. Turn to medium heat and toss gently with tongs until the pasta and sauce cling together. This takes about 1 minute. Add more pasta water if needed (see note 4). Add diced chicken to the pan and gently stir through. Season to taste with salt and pepper.
Remove from heat and serve right away! Garnish plates with fresh parsley and a sprinkle of cheese if desired.
Video
Notes
Note 1:To save prep time or if you prefer not to use onions, substitute with onion powder or skip it altogether. If you do use an onion, chop it very finely to ensure it sautés quickly and blends well into the dish. Larger pieces can be overpowering and crunchy.Note 2:Parmesan is crucial for the flavor of this recipe, so avoid shortcuts. Do not use canned or pre-grated cheese, as it won’t melt smoothly and will clump. Instead, use a block of cheese and grate it fresh on a microplane or fine grater. For an exceptional Alfredo, consider using Parmigiano Reggiano.Note 3: To check the sauce's thickness, it should coat the back of a wooden spoon. Lift the spoon and draw a line across the back with your fingertip. If the line stays clear, the sauce is thick enough. If not, simmer it a bit longer.Note 4:The Alfredo sauce should be silky smooth and cling to the pasta. If it becomes thick or grainy, simply drizzle in some pasta water and toss to smooth it out.Storage: For the best flavor, enjoy this Chicken Alfredo immediately after making it. If you have leftovers, store them in the fridge and add a bit of heavy cream or chicken broth when reheating. Keep in mind that the pasta may become softer, and due to the dairy, this dish is not suitable for freezing.