When I was little, when my family and I went to Bridgeman's to get tulip sundaes, the three of them got hot fudge, and I always ordered butterscotch. There's something magical when butterscotch sauce hits ice-cream. This recipe is amazing, and is extra awesome when used for Turtle Sundaes.
In dutch oven, heat all ingredients over high heat (except vanilla) to boiling.
Reduce heat to low, and let simmer for 5 minutes, stirring frequently.
Remove from heat, stir in vanilla.
Cool and pour into jars.