Place the chicken breasts between two sheets of plastic wrap and gently pound them to an even thickness, about ½ inch. In a shallow dish, combine the flour, salt, and pepper. Dredge each chicken breast in the flour mixture, shaking off any excess.​

In a large skillet, heat the olive oil over medium-high heat. Add the chicken breasts and cook for 4-5 minutes on each side, or until golden brown and cooked through. Transfer the chicken to a plate and set aside.​

In the same skillet, add the non-dairy margarine. Once melted, add the sliced mushrooms and cook for 5-6 minutes, stirring occasionally, until they release their moisture and begin to brown. Add the minced garlic and cook for an additional 1 minute.​

Pour the Marsala wine into the skillet, scraping up any browned bits from the bottom. Allow the wine to simmer for 2-3 minutes to reduce slightly. Add the chicken broth and stir to combine. Return the chicken breasts to the skillet, spooning some sauce over each piece. Reduce the heat to low, cover, and let simmer for 10 minutes.​

Remove the skillet from heat. Garnish the chicken with chopped fresh parsley and serve hot