Seriously, this recipe is ACCURATE! And easy! Check it out:
In a small saucepan over medium, combine the brown sugar and water. Bring to a gentle boil and cook, stirring often, until the mixture reads 240 F on a candy thermometer.
Stir in the butter, salt, vinegar and 1/4 heavy cream. Set aside to cool to room temperature.
Once the mixture has cooled, stir in the rum extract.
In a medium bowl, combine 2 tablespoons of the brown sugar mixture and the remaining 1/2 cup of heavy cream. Use an electric mixer to beat until just thickened, but not completely whipped, about 2 to 3 minutes.
To serve, divide the brown sugar mixture between 4 tall glasses (about 1/4 cup for each glass). Add 1/4 cup of cream soda to each glass, then stir to combine. Fill each glass nearly to the top with additional cream soda, then spoon the whipped topping over each.
It’s fairly easy! And if you chill the cream soda while you’re making the rest of it, it really tastes like the butterbeer in the park! Try it!
Found the recipe here.