Place the steaks between two sheets of plastic wrap; pound with a kitchen mallet to tenderize.
Melt the butter in a skillet over medium-high heat, and heat until it begins to smoke. Cook the steaks for 1 to 2 minutes on each side until they have browned. Pour brandy over steaks and carefully ignite. Once the flames burn off, remove steaks from the pan and set aside.
Cook the onion and garlic in the same skillet over medium heat until they soften. Stir in the red wine, steak sauce, Worcestershire sauce, salt, and pepper; mix well. Mix in the mushrooms, stir, and cook for about 5 minutes.
Meanwhile, coat one side of each of the steaks with 2 tablespoons of the Dijon mustard. Gently lay them on top of the sauce in the skillet, mustard-side down. Spread 2 tablespoons on top of the steaks. Cook 2 to 3 minutes per side. Remove the steaks from the sauce, and keep warm.
Stir the cream in to the mushroom sauce and bring to a gentle simmer. Reduce heat to medium-low, return the steaks to the sauce, and simmer for 1 minute more before serving.