Karen Tack's Chocolate Frosting

Place sugar and cream in a heavy-bottomed saucepan; bring to a boil over high heat, stirring constantly. Reduce heat to medium and simmer, without stirring, about 5 minutes.

Remove saucepan from heat and stir in chocolate until melted. Stir in butter and vanilla until well combined. Chill, stirring occasionally, until cooled completely.