Italians call young balsamic vinegar with pronounced acidity da insalata—vinegar to be used with oil as a salad dressing; or for pinzimonio, a vinaigrette used as a dipping sauce for raw vegetables. Each diner improvises his own pinzimonio from cruets of balsamic vinegar, olive oil, salt, and pepper in the middle of the table. Young balsamic vinegar is also used to spike pan sauces and marinades.
Middle-aged balsamic vinegar is a more viscous vinegar. Italians call it medio-corpo, and this medium-bodied vinegar is used to add finesse to sauces and braises at the end of cooking, to give dimension to risotti and pasta dishes, and to enhance mayonnaise and other sauces.
Very old vinegar is called extra-vecchio, and affectionately, il patriarca. It possesses flavors, texture, and complexity that only very long aging can confer. Extra-vecchio ennobles just about any food deserving of its company. It would be a waste to mix very old balsamic vinegar with other ingredients or to pair it with highly spiced foods or complicated flavors. Its sapid perfume is best released on warm or at least room-temperature foods. It stands best alone and reveals its full potential used sparingly on unadorned prime cuts of beef, fish, poultry, or veal. It's delicious on sautéed liver -- foie gras and old balsamico is a glorious combination; still, you won't be disappointed if you substitute fresh calf's liver or even duck or chicken. Unmarinated wild game is particularly well suited to a few drops of old balsamic vinegar -- loin of fresh venison, pigeon roasted pink. So is wild duck, as well as choice cuts of fish such as tuna, halibut, or sole. Certain fruits in their prime of ripeness deserve balsamic vinegar's benediction -- pears, wild strawberries, and peaches are exquisite, as are mild, creamy cheeses such as fresh ricotta. Perhaps the best way to enjoy old balsamic vinegar is to pour yourself a thimble glass full after dinner and savor it all by itself.