Image thanks to www.chefknifes.com
Heat stovetop to medium heat. In medium size saucepan add 3 cups of brown sugar, and 1 cup of water. Increase heat to medium-high and bring mixture to a boil. Using candy thermometer test to see if mixture has reached a boiling heat of 230 degrees F.
Step2
Remove from heat and add 1 tablespoon of butter, 1 tablespoon of vanilla, and mix thoroughly.
Step3
Cool at room temperature and beat with electric mixer until thick and creamy. Thin mixture with cream until it reaches desired consitency.