Look at any recipe for a savory dish and chances are it will start with this step: fry onions in a pan over medium heat. Onions--and their allium family relatives, shallots, garlic, chives, and leeks--are one of the most heavily used ingredients in cuisines all over the world. You'll rarely find them in the spotlight, though--except for when they are fried into rings or used to repel vampires. In this book, Martha Jay gives alliums their due, offering an illuminating history of these cherished plants that follows the trail of their aromas to every corner of the globe and from ancient times up to today.             Going back to the earliest recipes from ancient Mesopotamia, Jay traces the spread of alliums along trade routes through Central Asia and into ancient Greece and Rome. Likewise she follows their spread in East Asia, where they have become indispensable, and of course into Europe and the Americas, where the onion--and its odor--gave rise to the name "Chicago" and the leek became the national symbol of Wales. Celebrated, denigrated, prescribed, and proscribed, onions, garlic, and their relatives can be found--as Jay lavishly demonstrates--in the histories of peasants and kings, in cuisine and art, in tales of colonization and those of resistance, and in medicinal cures and magical potions alike. Her book is a welcome celebration of some of the most important ingredients in the world.