01 - Place each chicken breast between sheets of parchment paper and gently pound with a meat mallet to an even ½-inch thickness throughout.
02 - Combine the flour, kosher salt, and black pepper in a shallow dish. Dredge each pounded chicken breast in the seasoned flour, coating both sides evenly, then shake off any excess.
03 - Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Sear the dredged chicken breasts for 4 to 5 minutes per side until deeply golden brown and cooked through. Transfer to a plate and tent loosely with foil.
04 - Pour the remaining tablespoon of olive oil into the same skillet. Add the sliced mushrooms and sauté for 4 to 5 minutes until well browned. Stir in the minced garlic and cook for 30 seconds until fragrant.
05 - Pour the Marsala wine into the skillet, using a wooden spoon to scrape up any caramelized bits from the bottom of the pan. Let the wine reduce by half, about 2 to 3 minutes.
06 - Add the chicken broth to the reduced wine and mushrooms. Simmer for 3 to 4 minutes, allowing the flavors to meld and the liquid to concentrate slightly.
07 - Return the seared chicken breasts to the skillet, spooning the mushroom-wine sauce over the top. Simmer together for 3 to 5 minutes until the chicken is heated through and the sauce has thickened to a glossy consistency.
08 - Scatter the chopped fresh parsley over the chicken and sauce. Serve immediately while hot, alongside mashed potatoes, rice, or gluten-free pasta.