01 - Place each chicken breast between two sheets of parchment paper and gently pound with a meat mallet to an even ½-inch thickness throughout.
02 - Combine the flour, salt, and pepper in a shallow dish. Lightly dredge each pounded chicken breast in the seasoned flour, shaking off any excess coating.
03 - Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the dredged chicken breasts and cook for 4 to 5 minutes per side until golden brown and cooked through. Transfer to a plate and tent loosely with foil.
04 - Add the remaining tablespoon of olive oil to the same skillet. Sauté the sliced mushrooms for 4 to 5 minutes until deeply browned. Stir in the minced garlic and cook for 30 seconds until fragrant.
05 - Pour the Marsala wine into the skillet, scraping up any browned bits from the bottom of the pan. Let the liquid reduce by half, about 2 to 3 minutes.
06 - Pour in the chicken broth and bring to a gentle simmer. Cook for 3 to 4 minutes, allowing the flavors to meld and the sauce to begin reducing.
07 - Return the seared chicken breasts to the skillet, spooning the mushroom sauce over the top. Simmer for 3 to 5 minutes until the chicken is heated through and the sauce has thickened to a glossy finish.
08 - Transfer to warm plates, spoon the pan sauce and mushrooms generously over each chicken breast, and finish with a scattering of fresh chopped parsley. Serve immediately.