Queso en aceite, or cheese in oil, is a centuries-old Spanish trick for preserving cheese. The oil serves as a barrier against bacteria and other microorganisms, keeping the cheese safe to eat for many months (or even years) without refrigeration. After a month or so of “curing” in the oil, the cheese absorbs enough of it so that it takes on a soft, yielding texture, and its flavor blends with that of the oil. Because the oil tenderizes the cheese, this method can even be used to restore the texture of cheeses that have dried out and are too hardened to eat.
Use only a dry, hard, crumbly cheese such as Manchego, Parmesan, or even aged gouda or cheddar. Trim off the rind, and then cut the cheese into cubes or planks about ½ inch across. Pack the pieces tightly into clean Mason jars, leaving an inch of space below the rim of the jar. (Some cooks like to add dried herbs or spices, which will flavor the oil, but we didn't find their flavors noticeable in the cheese itself.) Cover completely with extra-virgin olive oil, making sure that the cheese is fully submerged—take care here, because any parts of the cheese that are not submerged will grow mold. Seal the jars, and then store at room temperature for up to six months. As the oil penetrates the cheese, its hard, pale core will diminish. After about a month, the oil will have penetrated to the center and the cheese will be fully softened.