Adapted from Huffington Post
Yields 4 servings
In a small saucepan, combine brown sugar with 2 tablespoons water. Bring to a boil over medium heat and cook until the mixture reaches 240 degrees F (115 degrees C) on a candy thermometer, stirring occasionally. If you don’t have a candy thermometer, bring to a gentle boil and turn off the heat after about a minute of cooking.
Turn off the heat and add the butter, salt, vinegar, and 1/4 cup heavy cream. Stir until smooth. Cool mixture to room temperature before using.
In a medium bowl, beat together the remaining cream (1/2 cup) with 2 tablespoons of the brown sugar syrup.
In each glass, mix together 1/4 cup brown sugar syrup with 1/4 cup cream soda. Pour in the rest of the cream soda until it is nearly to the brim of the glass. Top with whipped cream.
Found on my new fav blog The pastry affair