Pour the beef broth and wine into a large skillet, and stir in the mushrooms, shallot, garlic, lemon juice, and Worcestershire sauce. Simmer over medium heat , stirring frequently, until the mushrooms reduce in size, about 20 minutes. Season to taste with salt and pepper.

Skim off 2 tablespoons liquid from the mushroom mixture, and pour into a small bowl. Whisk in the flour and blend to make a smooth paste. Stir the flour mixture into the mushroom mixture. Cook and stir as sauce thickens. Repeat as desired , adding small amounts of more flour to make a thicker sauce. Stir in the parsley. Pour the sauce into a pan, and keep warm until needed.

Using the same skillet, melt the butter over medium heat. Place the tenderloin in the skillet, and cook over medium-high heat, turning once, until desired degree of doneness. Serve with mushroom sauce.