Season the chicken on both sides with salt and pepper. Place the flour in a shallow bowl and dredge the chicken in it. Shake off the excess.
In a large frying pan over medium-high heat, warm 2 Tbs. of the olive oil. Place 2 pieces of chicken in the pan and cook, turning once, until browned on both sides, 2 to 3 minutes per side. Transfer to a platter and keep warm under a tent of foil. Warm the remaining 1 Tbs. oil in the pan and repeat to brown the remaining chicken. Place that chicken under your foil tent as well.
Lower the heat to medium and add the bacon to the pan, saute for a couple minutes to render out some of the fat, then add the mushrooms to the pan. Saute until brown and liquid has evaporated. Season with salt and pepper.
Add Marsala to the pan and boil for about 30 seconds, then add the chicken stock and let it reduce slightly, for about a minute. Stir in the butter and return the chicken to the pan. Season with salt and pepper, to taste and sprinkle with chopped parsley. Serve.