Prep the chicken. Place the chicken breasts (2) between sheets of plastic wrap and pound to an even thickness (about ½ inch). Season both sides with garlic powder (1 teaspoon), onion powder (1 teaspoon), Italian seasoning (1 teaspoon), salt (1/2 teaspoon), and a few cracks of black pepper.
Sear the chicken. Heat the olive oil (2 tablespoons) in a large skillet over medium-high heat. Add the chicken and cook for 3–5 minutes per side, until golden brown and cooked to about 160°F (71ºC) internally. Transfer to a plate; the chicken will finish cooking later in the sauce.
Build the sauce base. Reduce heat slightly to medium. Add the butter (2 tablespoons) to the skillet. Once melted, add the garlic (8 cloves) and cook 30–45 seconds, just until fragrant — do not let it brown.
Toast the flour. Sprinkle in the flour (2 tablespoons) and stir constantly for 60–90 seconds, allowing it to cook out and lightly toast without darkening.
Deglaze + thicken. Pour in the white wine (2 tablespoons), scraping up any browned bits from the pan. Let it cook for about 30 seconds, then whisk in the chicken stock (1 cup), heavy cream (1 cup), and Dijon mustard (1 teaspoon). Simmer gently for 3–5 minutes, stirring often, until the sauce thickens slightly.
Add Parmesan off heat. Remove the pan from the heat and stir in the Parmesan cheese (1/2 cup) until fully melted and smooth. Return to low heat only to keep the sauce warm — do not boil.
Finish the dish. Return the chicken (and any juices) to the skillet and simmer gently for 2–3 minutes, until the chicken is cooked through and the sauce is silky.
Finish & serve. Sprinkle with fresh parsley (1-2 tablespoons) and a final crack of black pepper. Serve over mashed potatoes, pasta, or rice.