Add sugar, buttermilk, butter, and baking soda and turn stove to medium-high.
Continue to stir mixture and make sure the bottom isn't getting burned.
Once boil begins, add vanilla and keep stirring. Take syrup off heat and serve once it has cooled a little.
Tips
This is a recipe that is well known in my family! I would HIGHLY recommend that you try and use the best vanilla you can get your hands on. We have a container of vanilla bean paste that makes this incredible!