Karen's Famous Buttermilk Syrup

My sister introduced this yummy condiment to us, and we love it!

1 cube butter (melted)
3/4 C buttermilk 

2 C sugar

Bring to a boil (using a whisk). Immediately take off the heat. Stir in 1 tsp vanilla and 1 tsp baking soda; this doubles its volume.