Iron eggs are a traditional Taiwanese egg dish made from eggs that are repeatedly stewed in a mixture of spices and air-dried. The result is a dark, chewy and flavorful egg usually eaten as a snack. It is unlike other boiled eggs in that it has a very dark color which comes from the soy sauce used. They are sold by many Taiwanese street food vendors.
While the origins of iron eggs are not exactly known, they are thought to have originated in a dockside restaurant in New Taipei City. On a slow day the eggs had to be reboiled on numerous occasions as few people came in to buy them. The resultant egg was deliciously chewy due to the loss of albumin with repeated cooking and the delicacy was born.
Most commonly, iron eggs are made from chicken eggs, but any eggs, such as quail and duck, may be used. Iron eggs are not the only version of egg which is well-known in Taiwanese cuisine. Various other forms of eggs are found on menus and in restaurants throughout Taiwan. One of the most famous is the thousand year old egg, which claims it's the cheese counterpart of blue cheese.
Contrary to its name, the thousand year egg, one of a number of traditionally Chinese egg dishes, is not really a thousand years old. It is, in fact, an egg — chicken, duck or quail — that has been preserved in a mixture of lime, salt, ash and clay for some weeks to months. The result is that the white of the egg becomes dark and jelly-like and the yellow is a green color and turns a creamy consistency. Thousand year eggs, like iron eggs, are considered a delicacy.
Another well known Taiwanese egg dish is the salted duck egg. Traditionally these are made by placing the duck eggs in a mixture of salt and mud for an extended period of time. Nowadays the duck eggs are more commonly soaked in brine, resulting in a very salty, rubbery egg white and a creamy yolk.
The other commonly found Taiwanese boiled egg dish is tea eggs. These live up to their name and are just that — eggs boiled in tea. The result is a brownish boiled egg which has a hint of tea flavor. As with iron eggs, all of these eggs are popular as snacks or as accompaniments to a larger meal.