Balsamic Vinegar Reduction

Pour the contents of one bottle of balsamic vinegar into a heavy bottomed non-reactive saucepan (stainless steel works well). Bring the contents to a boil, and then lower heat to a simmer. (Because you’re dealing with vinegar and its fumes, be sure to turn on your kitchen exhaust fan. There’s no danger; it’s just that vinegar can be a strong odor.)

Continue simmering until the vinegar is reduced by about half. It should be slightly syrupy, similar to a glaze, and coat a spoon. Take the reduction off the heat when it is still just a bit thin. It will continue to thicken as it sits. Let the vinegar stand at room temperature until it is cool. Pour in wide-mouth container, and store in the refrigerator.

Before using, be sure to set the container out until it comes to room temperature, or, if necessary, heat it a bit in the microwave or set it in a warm water bath (similar to what you do with crystallized honey.) 

Use a spoon to drizzle desired amount. (Instead of making your own, you can purchase ready-made balsamic glaze at Trader Joe's and at many supermarkets.)