Combine the sugar and water in a medium-sized saucepan. Bring to a boil, stirring until the sugar has dissolved. Lower the heat to medium and allow the mixture to boil for 4 minutes.
Add the butter and stir until the butter has dissolved. Remove from the heat and add the extract if desired.
Let the syrup cool for 5 minutes before transferring to a pitcher or jar for storage. Serve immediately or store tightly covered in the refrigerator for up to a month.
Notes
To reheat, remove the lid and microwave in 15-second intervals, stirring in between until hot. Or place on a folded washcloth in a pan of water, bring to a simmer and using a hot pad, swirl the jar every so often until the syrup has warmed.