What is the name of the Chinese preserved egg with a dark, gelatinous yolk?

The Chinese preserved egg with a dark, gelatinous yolk is called a century egg. It is also known as a preserved egg, thousand-year egg, or pidan.

Century eggs are usually duck eggs, though chicken and quail eggs can also be used. They are preserved in an alkaline mixture traditionally involving clay, ash, salt, quicklime, and rice husks. The curing process can take several weeks to several months, not an actual century.

During preservation, the yolk becomes dark greenish-gray, soft, and creamy, while the egg white turns translucent brown and jelly-like. The distinctive aroma comes partly from chemical changes involving sulfur and ammonia. Century eggs are commonly served sliced, in congee, or alongside tofu.

A common myth claims that century eggs are soaked in horse urine or buried for 100 years; neither is true. The method is a preservation technique, and the name is an exaggeration referring to the egg's unusual aged appearance.