They're made by preserving duck or chicken eggs in ash, clay, salt, lime, and rice hulls for anywhere from a few weeks to a few months. The end result is an egg with transparent dark brown whites, an opaque, green-gray yolk, and a sulfurous, ammonia-like flavor. While the concept might sound nauseating, the taste, once acquired, is absolutely addictive. Have you come across a century egg? If so, what did you think of it?
Source: Flickr User azneecs