In Chinese and many other Asian cultures, pidan, or the century eggs are considered comfort food.
They are prepared by preserving duck or sometimes chicken eggs in a mixture of clay, ash, salt, quicklime, tea leaf and/or rice hulls for up to months.
The resulted alkaline fermented eggs defy the conventional knowledge about what a delicacy should look, smell or have chemical-wise. First-timers are often surprised to see its amber-brown jelly-like egg-white and greenish grey egg yolk. Its rotten smell comes from hydrogen sulfide and ammonia generated by protein denaturation. What's more, it has lead oxide, an important component to keep the eye yolk soft and prevent the egg-white from over-fermentation.
Like many other dangerous delicacies in the world such as pufferfish from Japan and Casu Marzu of Italy, the century eggs are not for the faint-hearted.
Source: ACSReactions via Youtube