Recipe courtesy of John Lettieri, Lettieri Espresso Bar Café.Yield is about 1 litre, serves 8.
Put the whey in an 8-litre pot on high heat.
When a candy thermometer reaches 86 degrees F. (for soft curds) or 90 degrees F (for firm curds), add the vinegar and salt and remove from the heat. This will take about 15 to 20 minutes.
Let the mixture sit for a few minutes, or until the curds form.
Remove the curds gently with a slotted spoon and put them in a cheesecloth-lined strainer over a bowl to cool.
Cool to room temperature, transfer to a container, cover and refrigerate.