Up your cocktail game with this book of classic and nouveau bourbon recipes. Bourbon has experienced a renaissance in recent years, to the point where some brands are actually becoming hard to find. The problem is the aging. When demand increased, bourbon distillers just couldn’t put some more mash in the still. To get bourbon’s distinct flavors, it has to be aged in new, charred oak barrels. While there is no minimum aging period — some swill is aged for as little as three months — the good stuff is in the barrel for at least two years. Any bourbon aged less than four years must have that disclaimer on its label.