1. In a shallow dish, combine flour, 1/2 teaspoon salt, and 1/4 teaspoon pepper; mix well. 2. In a large skillet over medium heat, heat oil and melt 1 tablespoon butter. Coat chicken on both sides in flour mixture. 3. Saute chicken 3 to 4 minutes per side, or until golden. Remove to a plate. Add remaining butter, the onion, and mushrooms to skillet and saute 5 minutes, stirring occasionally. Add wine, broth, garlic powder, remaining salt and pepper, and remaining flour mixture, and whisk until smooth and sauce begins to thicken. 4. Return chicken to skillet and cook 3 to 4 minutes, or until no longer pink in center and heated through. Serve topped with sauce.