Butterbeer

I would describe the taste of this butterbeer
as a kind of shortbread and butterscotch.

Ingredients:
1 cup light or dark brown sugar
2 tablespoons water
6 tablespoon butter
1/2 teaspoon salt
1/2 teaspoon cider vinegar
3/4 cup heavy cream, divided
1/2 teaspoon rum extract
Four 12-ounce bottles cream soda

Directions:
In a small saucepan over medium heat,
combine the brown sugar and water.
Bring to a gentle boil and cook,
stirring often, until the mixture
reads 240 degrees F. on 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.
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 on the whipped topping.