Place the steaks between two sheets of plastic wrap and pound with a meat tenderiser.
Melt the butter in a frying pan 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 frying pan over medium heat until softened. Stir in the red wine, 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 each. Gently lay them on top of the sauce in the frying pan, mustard-side down. Spread 2 tablespoons mustard on top of each of the steaks. Cook 2 to 3 minutes per side. Remove the steaks from the sauce and keep warm.
Stir the cream into 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.