Butterscotch sauce has a sweet, buttery, and rich flavor that makes it ideal to pour over ice cream, pancakes, waffles, or enjoy straight out of the jar.
Using a 2 to 3-quart heavy-bottomed saucepan over medium heat, add the butter and stir until melted.
Whisk in the brown sugar and heavy cream. Continue to whisk just until the sugar dissolves. Stop whisking and allow the mixture to boil for 4 minutes. Do not stir.
Remove from the heat and stir in the vanilla extract. Allow the butterscotch sauce to sit for 10 to 15 minutes. Pour into a ½ pint mason jar. The longer the sauce sits, the thicker it will get.