Pour balsamic vinegar into a saucepan.
Turned the stove to medium heat to bring to a boil.
Then, reduce to a simmer while stirring occasionally for 15-20 minutes.
Once balsamic reduction reaches a syrup consistency, completely remove from heat.
Note, keep an eye on the balsamic since it can burn quickly.
The sauce will continue to thicken as it cools.
If reduced too long, the reduction may harden. Add a bit of water to thin it back down if needed.