In taking the measure of a good home cook, many Italians might agree that among the criteria there would have to be the quality of the potato salad. Not that there is any mystery about what goes into it: It's just potatoes, salt, olive oil, and vinegar. No onion, eggs, mayonnaise, herbs or other curiosities. But the choice of potatoes has to be right. Their flesh must be waxy smooth and compact, not crumbly; their color when cooked, warm and golden, like that of maize or country butter; their flavor fresh, sweet, and nutty, with no hint of mustiness. They should be boiled until fully tender, but without the least trace of sogginess. The slices must come off the potatoes whole, without breaking apart. They must be splashed with good wine vinegar when they are still hot so that they can soak up the aroma while their heat softens the vinegar's acetic edge.
