In a medium bowl combine chicken broth, wine, thyme, garlic powder and pepper. Add mushroom slices; toss to coat. Cover and set aside. In a large nonstick skillet melt butter over medium heat. Add steaks and cook for 8 to 10 mins for medium rare and 10 to 12 mins for medium, turning once. Remove from skillet; cover and keep warm. Add onion to skillet; cook for 3 mins, stirring occasionally. Stir in flour and salt; cook and stir for 1 min. Pour mushroom mixture into skillet. Bring to boiling. Boil gently, uncovered, for 10 to 12 mins or until sauce is thickened and mushrooms are tender, stirring occasionally. Return steaks to skillet; cook about 1 min more or until heated through. Makes 6 servings.