Place full cream milk, natural yoghurt and milk powder (optional) into mixing bowl and warm 6 min/50°C/speed 3. Transfer into a thermal serving bowl or other large bowl and set aside or transfer into 8 sealable jars or containers and wrap immediately in a blanket to keep warm. Leave thermal serving bowl or jars undisturbed for 11-13 hours at room temperature, then chill in refrigerator for at least 3 hours before serving.