Add your brown sugar and water to a pan on a medium heat and stir thoroughly until sugar has dissolved. Bring to a gentle boil and then add your cider vinegar and cream. Stir thoroughly. Then remove from the heat.
Mix in butter and your rum and set aside.
Add 300ml of cream to a mixing bowl along with 2 tsp on butterscotch sauce. Using an electric whisk, whisk your cream until your get soft peaks. Set aside.
Grab yourself a suitable glass and fill 1/5 way with your sugar cream mix. Then fill to the top with cream soda. Top with your butterscotch cream and drizzle over additional butterscotch sauce.