bring the brown sugar, corn syrup and butter to a boil
boil until the syrup reaches 240 degrees (remembering to adjust temperature for altitude)
take off the heat and let cool 5 mins, then stir in the whipping cream, apple cider vinegar and rum extract
let cool completely
Frozen Butterbeer
stir 2 Tbsp into every 12 oz of cold cream soda - or 3/4 C into a full 2 liters
Freezing 3 options
a - run through an ice cream maker for 25 mins
b - pour into a large container and place in the freezer, stir ever 20 mins for 2 hours or more until slushy
c - freeze 2/3rd of the cream soda in an ice cube tray overnight - mix the ice cubes, with some cold cream soda (1/3) and the syrup and blend with a hand blender
Topping
beat the marshmallow creme, heavy whipping cream along with 2 Tbsp of the butterscotch syrup together
pour the butterbeer into a glass and add some of the topping