Pour balsamic vinegar into a small saucepan.
Bring the balsamic vinegar to a boil over medium-high heat. Turn the heat down to low and simmer for approximately 10 minutes, until the balsamic reduces to a syrup that easily coats the back of a spoon. Watch carefully toward the end to ensure it doesn't burn.
Remove from heat and cool.
Store in an airtight container for up to two weeks.