Century egg is original from China. It has no vitamin, but it is delicious, and I like eating it.
I don't know how to make it. Mostly, I buy it from market.
Century egg sold in Cambodia is easy to recognize. It has light red shell like in photo. Inside is dark and it has not good smell anyway.
In general, I eat this egg with rice, and I add fish sauce. Some people like eat it with soybean sauce.
This egg can be added into soup or made to another kind of food.
When I buy, I have to tell seller that I need cooked century egg. It is like ordinary egg. If it is uncooked, or not cooked yet, it has liquid inside. If it is well cooked, it will be as same as normal cooked egg.
If you buy it, you should confirm from the seller that it is cooked or not yet.