Heat up the cream in a double boiler to 85 degrees C (you will need a thermometer for best results). Add tartaric acid and stir 5 minutes until cream starts to break up into curds. If no curds form, add a pinch more tartaric acid but don't add too much or it will be grainy.
Line a colander with cheesecloth or muslin. Using a slotted spoon, transfer the curds to the colander. Fold over the cheesecloth and let drain 1 hour.