Huitlacoche, also known as the "Mexican truffle," is an edible fungus that forms on undeveloped corn ears and sells for as much as $40 a pound. Discovered by the Aztecs, the bulbous fungus has been consumed in Mexico for centuries and has recently become a popular specialty ingredient around the world. However, the US has dedicated significant time and money to keeping its cornfields free of what it calls "corn smut" and "the devil's corn." Huitlacoche forms naturally during the rainy season, but farmers can also inject the fungus into their cornfields to harvest the valuable "black gold." So, why has huitlacoche become so popular, and what exactly makes it so expensive?