Sprinkle chicken with salt and pepper. Dust with flour; shake off excess. Melt 3 tablespoons butter in large skillet over medium-high heat. Add chopped sage; sauté 1 minute. Add half of chicken. Sauté until brown and cooked through, about 3 minutes per side. Transfer chicken to platter. Repeat with remaining butter and chicken. Tent chicken with foil. Add Marsala and broth to skillet; bring to boil, scraping up any browned bits. Boil until sauce is reduced to 1/2 cup, about 10 minutes. Season with salt and pepper; spoon over chicken. Garnish with sage leaves.