Heat milk and, if desired, whipping cream in a saucepan over medium heat to 190°. (Do not boil.) Add buttermilk, stirring until large curds form.
Line a colander with several layers of cheesecloth or a coffee filter; pour mixture into colander. Let stand 20 to 30 minutes to drain. Press cheese mixture slightly to remove remaining liquid.
Invert cottage cheese onto a serving dish; sprinkle with salt. Cover and chill 8 hours. Serve with fresh fruit, if desired.