Directions:
Start by placing each chicken breast between two sheets of parchment paper and gently pounding them with a meat mallet until they are about 1/4 inch thick. Season both sides of the chicken breasts with salt and pepper.
Next, pour the flour into a shallow plate and dredge each chicken breast in the flour, shaking off any excess.
Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Once hot, add the chicken breasts to the skillet and cook for 2-3 minutes on each side, until they are golden brown and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add another tablespoon of olive oil if needed, then add the sliced mushrooms. Cook the mushrooms for 5-7 minutes, until they are golden brown and all the liquid has evaporated.
Pour the Marsala wine into the skillet and stir, scraping up any browned bits from the bottom of the pan. Allow the wine to cook for 1-2 minutes, until it has reduced slightly.
Add the chicken stock to the skillet and bring the mixture to a simmer. Let it cook for another 2-3 minutes, until the sauce has thickened slightly.
Return the chicken breasts to the skillet, along with any juices that have accumulated on the plate. Simmer for another 2-3 minutes, until the chicken is heated through and the sauce has thickened further.
Remove the skillet from the heat and swirl in the butter until it has melted and incorporated into the sauce. Season with additional salt and pepper to taste.
To serve, place a chicken breast on each plate and spoon the mushroom Marsala sauce over the top. Garnish with chopped fresh parsley for a pop of color and flavor.