1. Microwave semisweet chocolate morsels and whipping cream in a 2-qt. microwave-safe bowl at MEDIUM (50% power) 2 1/2 to 3 minutes or until chocolate begins to melt.
2. Whisk until chocolate melts and mixture is smooth. Whisk in butter; let stand 20 minutes. Beat at medium speed with an electric mixer 3 to 4 minutes or until mixture forms soft peaks. Use immediately.