Pour 1 cup balsamic vinegar into a small saucepan
Add 1 to 2 tablespoons sugar or honey, if desired
Bring to a gentle boil over medium heat
Reduce heat to low
Simmer for 10 to 20 minutes, stirring occasionally
Cook until the vinegar is reduced by about half and coats the back of a spoon
Remove from heat and let cool
Use immediately or store in a sealed container in the refrigerator