Veal medallions with vegetables and mustard sauce

Brown the veal medallions on both sides in butter for about 5 minutes. Meanwhile, slice the mushrooms. Wrap the medallions in aluminum foil and set aside. Drain the fat from the pan but leave the leftover browned bits of meat. Add a rounded tablespoon of butter to the pan. Fry the mushrooms until all the liquid has evaporated. Add 3 tablespoons of mustard, 3 tablespoons of water, and 3 tablespoons of light soy sauce. Keep stirring until you have a homogenous sauce. Push the mushrooms off to one side of the pan and add the spinach next to them. Cover the pan with a lid and allow the spinach to wilt. 

Return the meat to the pan along with any juices that have been released from the meat. Heat everything through and serve.