Balsamic Glaze or Balsamic Reduction Sauce

A few years ago at a highly acclaimed Denver restaurant, I ordered a dish of crab cakes that were served drizzled with a wonderful balsamic glaze. One bite and I was inquiring the waitress for a recipe or method to make the glaze. She exclaimed it to be incredibly easy "Just bla..bla..bla.. then bla..bla.. and then just bla and voila and you've re-created an exact replica of this glaze that is sitting in front of you".