Pour 1/2 gallon of lightly-soured milk into a pan. Heat milk to 185 degrees. (Don't heat higher than that or the curds may become an unpleasant texture.)
NOTE: If 1 tablespoon of vinegar doesn't separate the curds enough, you can add vinegar 1 tablespoon at a time every 2 minutes or so until you get the separation you need and whey is almost clear.