Preparation Combine chocolate and butter in a medium bowl. Bring cream and corn syrup to a boil in a small saucepan over medium heat, stirring often. Pour over chocolate; let stand 1 minute, then stir until melted and smooth. Let cool to room temperature, about 1 hour. DO AHEAD: Can be made 3 days ahead. Cover and chill. Return to room temperature before using.
Preparation Combine chocolate and butter in a medium bowl. Bring cream and corn syrup to a boil in a small saucepan over medium heat, stirring often. Pour over chocolate; let stand 1 minute, then stir until melted and smooth. Let cool to room temperature, about 1 hour. DO AHEAD: Can be made 3 days ahead. Cover and chill. Return to room temperature before using.