Step 1

Combine the brown sugar and buttermilk in a medium-sized saucepan over high heat. Whisk or stir to combine and bring to a boil, stirring often.

Step 2

Reduce heat to low or medium-low and simmer for 3-4 minutes, stirring occasionally, until the sugar has dissolved and the syrup has thickened.

Step 3

Add the butter and stir to melt. Remove from the heat. Add the vanilla and baking soda. Whisk or stir well to combine. Let cool for at least 10 minutes before serving.