Start with 1 cup of balsamic vinegar in a small saucepan. I don’t typically add any sweetener, but if you want, you can add a tablespoon of brown sugar, honey or maple syrup. Bring it to a boil over medium-high, then reduce to medium-low and simmer. You can gauge when it’s ready if it coats the back of a spoon. How far you reduce it is up to you, but keep in mind that it will thicken as it cools.