For perfectly balancing the flavors of a dish, acidity is a cook's trump card: Tart fruit juices and vinegars bring an instant brightness to braises, sauces, and vinaigrettes. Any one of these tangy ingredients will give new flair to your cooking.
Alvear Vinagre de Pedro Ximénez Semi Seco Solera 10 (Spain) - Flavorful and punchy, this Sherry wine vinegar is aged in wood for ten years. Ideal for finishing braised greens or ribs. ($35 for 9 ounces; tienda.com)