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 - In a shallow bowl, whisk together the flour, salt, and black pepper until evenly combined. Dredge each pounded chicken breast in the seasoned flour, coating both sides lightly, then shake off any excess.
03 - Heat 2 tablespoons of olive oil in a large skillet over medium-high heat until shimmering. Carefully lay the dredged chicken breasts in the pan and cook for 4 to 5 minutes per side until a deep golden crust forms and the internal temperature reaches 165°F. Transfer the chicken 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 deeply browned and most of their moisture has evaporated. 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 all the caramelized browned bits from the bottom of the pan. Let the wine reduce by half, approximately 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 liquid to reduce slightly.
07 - Return the seared chicken breasts to the skillet, spooning the mushroom-wine sauce generously 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 - Sprinkle the chopped fresh parsley over the top and serve immediately while hot, alongside mashed potatoes or gluten-free pasta if desired.