The dish consists of small eggs that have been repeatedly stewed in a mix of spices and air-dried. The resulting eggs are dark brown on the outside, chewy in texture, and very flavourful compared to standard boiled eggs. It has been said to taste "sweet, spicy and slightly salty with a concentrated egg flavour—a great snack with drinks".
The eggs were supposed to have been created by the restaurateur Chang-nian Huang (黃張哖) serving snacks to the dock hands in the sea-side town.[when?] On one rainy day with less business than usual, Huang Zhangnian had to continually recook soy eggs (滷蛋) to keep them warm after taking them out of the soy sauce broth. The recooking and drying process eventually resulted in shrunken eggs that were dark, flavourful, and chewy, which was extremely popular with the locals. Huang eventually founded a new business based on her iron egg recipe, selling them under the brand Apotiedan (阿婆鐵蛋; 'Grandma's iron eggs'). They can only be created by the use of "chicken, pigeon or quail eggs" but not from duck eggs. Quail eggs are very popular. The popularity of iron eggs has risen and they can be found in other regions besides Taiwan, such as in Africa and the Middle East.
- Smoked egg – Food that involves the smoking of eggs
- Taiwanese cuisine – Culinary traditions of Taiwan
- Tea egg – egg boiled in tea as a savory snack
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- 林明峪 (1983). 大快朵頤 (in Chinese). 聯經. pp. 21–5.
- Newman, Jacqueline (2006). "Iron Eggs". Flavor and Fortune. Institute for the Advancement of the Science and Art of Chinese Cuisine. 13 (1): 5, 8.
- Hiufu Wong, Maggie. "40 of the best Taiwanese foods and drinks". edition.cnn.com. CNN. Retrieved 8 April 2020.