In a double boiler, heat the single cream to 85 degrees C (use a thermometer for best results). Add 1/8 teaspoon tartaric acid to the heated cream. Stir constantly for about 5 minutes until the mixture thickens and you see tiny flecks of curd. (If you don't see curds forming, add a tiny pinch more of tartaric acid and stir for another five minutes. Don't add too much tartaric acid at once, or your cheese will become grainy.)
Line a sieve with muslin or cheesecloth. Using a slotted spoon, transfer all of the curds from the saucepan to the muslin-lined sieve. Fold the muslin over the curds and leave at room temperature for 1 hour to drain.
Enjoy immediately or place the finished cheese in a covered container and refrigerate for up to 2 weeks.
You can find tartaric acid sold online or in speciality shops, such as those specialising in confectionery or home-brewing.