Beef Tenderloin in Mushroom Sauce - With meat

1 (3 lb) beef tenderloin 1 tablespoon onion , minced 3 tablespoons butter 2 cups mushrooms , sliced 2 tablespoons all-purpose flour 1 cup beef broth 2[...]

1 teaspoon vegetable oil 4 tablespoons butter or 4 tablespoons margarine , divided 2 beef tenderloin steaks (1 inch thick) or 2 beef tenderloin fillets (1[...]

4 (4 ounce) beef tenderloin steaks , trimmed (1/2-inch thick) 1/2 teaspoon black pepper 1/4 teaspoon salt 1 cup sliced mushrooms 1/2 cup finely chopped onion[...]