Spread each slice of meat, slather 1 side with mustard, and cut in half.
Sprinkle both sides with flour.
Line the meat in a frying pan without oil, and cook on both sides until golden brown.
Add the soy sauce and mirin once the meat has browned, and coat the meat with the sauce as it cooks. Work quickly so that it doesn't burn!
Story Behind this Recipe
This tasted great when I slathered mustard in between!
The sauce will thicken when you add the flavoring ingredients since the meat is coated with flour. It will also burn easily at that point, so coat the meat briskly with the sauce. This is well seasoned, so adjust to suit your tastes.