Start a medium pot of water about half to 2/3 full on high on the stove to bring it to a boil for the pasta.
As the water boils, prep the chicken and preheat the oven to 350. Flatted out each piece of chicken and cut in half long ways. Cover the cut pieces of chicken with plastic wrap and pound the pieces until they are about .5 of an inch thick. This should give you 4 thin pieces of chicken.
Season the chicken on both sides with salt, pepper and garlic powder.
Once the oven is preheated, place the chicken on a greased cookie sheet and cook for about 15 minutes or until 165 degrees.
Once the pasta comes up to a boil, place pasta in the boiling water and turn down the water to medium high. The noodles cook for about 8 minutes.
While the chicken and pasta is cooking, start on the sauce. Cut the butter into chunks and place all except 1 tbsp in a deep frying pan on medium heat. Once the butter melts, sprinkle about 2 tablespoons of flour on the butter and 2 tbsp minced garlic. Stir until you have a thick paste. If you don't have a thick paste, add a little more flour.
Once you have a thick paste, slowly whisk in the milk and heavy whipping cream. Keep whisking until all of the flour mix has been stirred in. Add 1/2 tsp salt and 1 tsp garlic powder. If needed, add extra garlic powder & salt to taste. Let this come to very light simmer.
Once the sauce bubbles turn off the heat, and put about 3/4 cup of parmesan into the sauce. Stir to incorporate the cheese. If the sauce seems too thick, feel free to add a little more milk.
Drain your noodles and cut your chicken into slices.
Serve right away to get the best alfredo consistency and top with remaining parmesan and parsley, if desired. If it sits on the stove for a while, give it a whisk and add more milk if needed. It gets thicker as it sits.