In a medium saucepan, combine the brown sugar and water.
Over medium high heat, stir until sugar is dissolved and bring to a boil.
Reduce the heat to medium and boil for 5 minutes.
Add the butter and stir for 1 more minute while mixture just barely boils.
Remove from heat and add the extract.
Allow to cool for 5 minutes before using or transferring to jar for refrigerator storage.
