Melt butter, sugar, and buttermilk in a medium saucepan until the butter is melted. The mixture will boil up high so you need a pan with room for it to do this. Next, bring the mixture to a boil and boil for one minute.
Remove from heat and whisk in the vanilla and baking soda. The mixture will foam! Serve warm on pancakes or waffles. Store leftover buttermilk syrup in an airtight container in the fridge.
Notes
You can make this ahead of time and warm gently to serve. Store in the fridge.
BUTTERMILK SUBSTITUTE
Although real buttermilk is ideal, if you don’t have buttermilk you can add 1 tablespoon of vinegar or lemon juice to each cup of milk and let it sit for a couple of minutes.Source: my sister Shelly has made this forever