Flour the pieces of meat lightly. Melt the butter in a nonstick frying pan over medium heat. Saute the meat for about 3 minutes on each side, until reddened. Remove the steaks and keep them warm.
Pour the broth into the pan, increase the heat until the liquid boils and the remnants of meat stuck to the bottom are peeled off. Add the ginger and boil for 2 minutes, stirring constantly.
Add the mustard and onion, salt and black pepper to taste. Serve the steaks with this sauce.