How to Make It
Place powdered sugar in a large bowl. Melt salted and unsalted butter in a small saucepan over low heat. Add brown sugar and cream, whisking until all lumps are dissolved. Bring to a boil over medium heat. Remove from heat; stir in vanilla.
Pour hot butter-cream mixture into powdered sugar; beat at high speed with an electric mixer 2 minutes or until blended. Cool 1 hour, stirring occasionally.
Southern Living Off the Eaten Path; Uncle Lou's Southern Kitchen, Memphis, Tennessee