Add all of the ingredients, except the vanilla into a small saucepan over medium heat and stir until the sugar has completely dissolved. Then turn the heat up and bring to a boil.
Continue to stir while the mixture boils for about 3-4 minutes. Then turn off the heat and stir in the vanilla (it may bubble up, so be extra careful).
Let cool for a few minutes and then pour into an airtight container.
Notes
The chocolate syrup will stay good in the refrigerator for up to a month. I like to store it in mason jar, being sure to clean the lid well after each use.Use the chocolate syrup in this Iced Mocha recipe for a coffee shop experience right in your own kitchen!