Century Egg

Homemade Century Eggs (Pidan)

A traditional Chinese preparation in which duck eggs are cured in an alkaline clay paste for several weeks, transforming the whites into translucent amber jelly and the yolks into a creamy, dark green centre with a deep savoury-sulphurous flavour. The method below is a home-scale adaptation using a strong alkaline brine, since most home cooks cannot source the traditional wood-ash and lime paste.

Prep

30 min

Total

30 min

Serves

6 eggs

Difficulty

Hard

Recipe ingredients

• •6 whole duck eggs, fresh, very clean, uncracked shells
• •55 g (¼ cup) food-grade slaked lime (calcium hydroxide), also called pickling lime; do NOT substitute with garden lime
• •30 g (2 tbsp) food-grade soda ash (sodium carbonate), washing soda, food-grade only; do not confuse with baking soda or caustic soda
• •10 g (2 tsp) fine sea salt
• •200 ml (¾ cup + 1 tbsp) strong black tea, cooled, Lapsang Souchong or any robust black tea; traditional bags of tea leaves also tied into the clay
• •300 g (10½ oz) wood ash or rice husk ash, optional but traditional; if omitted, increase the clay paste so the eggs are fully buried; use only ash from untreated wood
• •60 g (¼ cup) rice flour, to bind the paste, or use plain wheat flour

Steps

1. 1 SAFETY FIRST: Food-grade calcium hydroxide and soda ash are strongly alkaline and can burn skin and eyes. Wear rubber gloves and safety glasses for the entire preparation and do not let either powder come into contact with your face. Keep the workspace clear of children and pets.
2. 2 Inspect each duck egg against a bright light to confirm it is uncracked and fresh. Discard any with hairline cracks. Wash the shells gently in warm water with a little salt, then dry them completely; any moisture on the shell will interfere with the cure.
3. 3 To make the alkaline paste, sift the slaked lime, soda ash, salt, rice flour and ash (if using) into a large non-reactive bowl. Slowly pour in the cooled tea, stirring with a wooden spoon, until a thick paste forms similar to wet clay. It should hold its shape when pressed and not run; add more rice flour or tea as needed.
4. 4 Line a wide-mouthed glass or food-grade plastic container (a 1 L jar or a large kimchi tub works for 6 eggs) with a 2 cm (¾ in) layer of the alkaline paste.
5. 5 Lay the first egg on the paste, then pack more paste around and over it until completely buried, leaving no shell exposed. Repeat with the remaining eggs, stacking if needed and ensuring at least 2 cm (¾ in) of paste above the top egg. Press out air pockets with the back of a spoon.
6. 6 Seal the container with a tight lid. Label with the date. Store at a steady 15–20 °C (60–68 °F), away from direct sunlight and heat. Do not refrigerate; the cold will stop the cure. Traditional Chinese home curing rooms sit around 18 °C.
7. 7 Leave the eggs undisturbed for 21 days for small duck eggs, 28 days for large ones, turning the container upside-down once a week to redistribute any liquid. Do not open the lid during curing unless you suspect a problem.
8. 8 At the end of the curing time, lift one egg out and rinse off the paste under cool running water. Crack it into a bowl to check: the white should be a glossy, translucent amber-brown jelly with no runny patches, and the yolk should be a creamy dark green with a slightly softer centre when cut. If the white is still milky, rewrap and cure for another 5–7 days. If the yolk is chalky-yellow, the cure is too short; if the egg smells sharply ammoniacal or the yolk is mushy-black throughout, discard the whole batch as over-cured.
9. 9 Once the egg passes the test, unwrap and brush all paste off the remaining eggs. Rinse briefly, pat dry, and store, uncovered or loosely wrapped, in the refrigerator for 1 to 2 weeks to mature the flavour and firm the yolk. Properly cured and chilled, they keep for several weeks more.
10. 10 SAFETY CHECK BEFORE SERVING: A fully cured century egg must have a jellied, translucent white and a yolk that is dark green to grey-green. Do not eat any egg whose white is still white or milky, whose yolk is yellow or bright orange, or that has any off, faecal, or rotting odour. If in doubt, discard it.
11. 11 TO SERVE: To eat a century egg safely at home, bring a small pot of water to a rolling boil and lower the room-temperature egg in gently. Simmer for exactly 4 to 5 minutes (centre should reach 70 °C / 158 °F on an instant-read thermometer). Cool under cold water, peel, and use within 24 hours.
12. 12 Classic presentation: slice the peeled egg into eighths and arrange on a plate with a mound of silken tofu dressed with soy sauce, toasted sesame oil, a little of the curing brine or a pinch of sugar, and sliced scallions; or stir diced pieces into congee in the final minute of cooking.