In a large saucepan, combine the sugar, cornstarch, coffee and butter until blended. Stir in milk. Bring to a boil over medium heat; cook and stir until thickened, 2 minutes. Remove from heat; stir in vanilla. Cool completely. Stir in condensed milk. , In a large bowl, beat cream until stiff peaks form; fold into milk mixture. Pour into a 9-in. pan. Cover and freeze until firm, 6 hours.