In a medium saucepan, over medium heat, melt the butter and stir in the brown sugar.
The darker the brown sugar you use, the deeper the flavor of your sauce.
Cook the brown sugar and butter until it begins to foam; then add the whipping cream, vanilla extract and salt.
Bring to a slow simmer, for about 7 minutes, but no longer.
Remove from stove and allow the sauce to cool completely before serving.
Store leftover sauce in a mason jar, or other sealed container, in the refrigerator, for up to 2 weeks.
