1Stir the brown sugar and water together in a saucepan over medium heat and bring to a gentle boil and cook until the mixture reads 240 degrees F on a candy thermometer.
2When a small amount of the syrup is dropped into a glass of cold water, it should form a soft ball.
3Next add the canna-butter, salt, cider vinegar, and 1/4 cup heavy cream, and stir then remove from heat and set aside to cool completely and then
4mix the rum extract into the cooled mixture.
5Combine 2 tablespoons of the brown sugar-cream syrup with remaining 1/2 cup heavy cream in a non-plastic bowl and beat with an electric mixer until whipped and cream holds soft peaks for at least 2 to 3 minutes.
6Pour about 1/4 cup of the remaining brown sugar-cream mixture into a tall glass and stir about 1/4 of a bottle of cream soda into the cream mixture.
7Top with the remainder of the cream soda in the bottle then top with about 1/4 of the whipped cream then repeat the process with 3 more glasses to serve to your very lucky guests!