When people see preserved eggs (pei daan, also known as thousand-year-old eggs) for the first time they are usually fascinated or repelled. I think they're beautiful: the different layers of colour of the 'white' ranging from deep amber to translucent black contrasts with the concentric, greenish-grey rings of the soft yolks. They are aged for only about 100 days after being cured in a mixture of earth, ash, slaked lime and tea.
Pei daan and another type of preserved egg, haam daan (salted egg), are unique to Chinese cuisine. Pei daan are sold coated in a beige or sandy-coloured clay and rice husks, while haam daan are coated in black, charcoal-like ash. They are either duck or chicken eggs. Shake the haam daan before buying to make sure it is solid - if you feel the yolk sloshing around the interior will have shrunk, meaning the egg is too old. The coating of both must be scraped off before use.
Pei daan can be eaten raw. Crack the shell and peel it, then serve the egg with soy sauce, sesame oil or sliced pickled ginger. Haam daan must be cooked before eating. Most of the salt is concentrated in the white, which some people discard, preferring the yolk. A boiled haam daan drizzled with sesame oil and eaten with plain white rice or congee is perfect Chinese comfort food.
Thousand-year-old eggs are delicious in congee. Peel the eggs and chop into small chunks. When the congee is almost fully cooked, stir the pei daan into the rice and add marinated sliced pork or minced beef. Serve with white pepper and chopped spring onions.
Pei daan is also good in Chinese steamed custard. Whisk plain eggs and add an equal volume of light broth or water. Season with a little soy sauce, salt and white pepper then stir in chopped pei daan. Steam in a heat-proof dish until just set - the custard should be slightly wobbly in the centre. Sprinkle with spring onions and drizzle with soy sauce and sesame oil.
The yolk of salted egg makes a rich and oily dish when fried with crabs or shrimp. If using crabs, clean them and chop into large pieces (with shrimp, just rinse them and leave the heads and shells on). Dust the crab or shrimp with flour. Heat about 250ml of oil in a wok and fry the crab or shrimp until the shells turn pink. Remove from the wok and pour off most of the oil.
Peel the raw, salted eggs. Discard the whites and mash the yolks with a fork. Cut a few slices of fresh ginger and cut spring onions into three-centimetre lengths. Heat the wok and fry the ginger and spring onions in oil. Add the yolks and fry until hot and bubbling. Return the shrimp or crab pieces to the wok and stir to coat with the egg. Garnish with chopped spring onions and serve.