The proliferation of cheap balsamic vinegar has prompted its excessive use. I have seen recipes that instruct one to “reduce ½ cup balsamic vinegar.” For one thing, a half cup of real balsamic vinegar would have been considered a young girl’s dowry in the aristocratic families of Modena. Furthermore, no reduction of balsamic vinegar should ever be necessary. I am not suggesting that only the $150 perfume-sized bottle of balsamic vinegar should be used in this recipe (or any other), but there is no point in using something that costs $3.99 for a half liter either. Look for something in the medium price range, perhaps $25 to $40 for an 8-ounce bottle. You do not need to use much, and it should always be added at the end, off the heat, so as not to lose its precious aroma.