Antonin Carâme's invention of the classic soufflé in the early 1820s was made possible by new ovens, which were heated by air drafts instead of by coal. This new technology provided the more even cooking temperature needed for a soufflé to rise properly and stay risen. Initially, Carême made his soufflés in stiff pastry casings that were not eaten. Their straight sides were the inspiration for our current soufflé dishes. He went on to create hundreds of other soufflés including the Soufflé Rothschild, which originally contained real gold and was aptly named by its creator in honor of his employer, at the time the richest man in France. It consisted of a pastry-cream base lightened with beaten egg whites and flavored with chopped crystallized fruits macerated in Danziger Goldwasser, a liquor containing suspended gold crystals. More modern recipes often substitute Kirsch or Cognac.