Century eggs.

A century egg, khai yiao ma in Thai, is a duck egg preserved for several weeks in an alkaline mixture. Old recipes used clay, ash, lime and salt. The egg doesn't need cooking. Peel it and the white has turned into a firm, see-through jelly, dark amber to brown, while the yolk is soft, creamy and grey-green. The smell is strong when you first peel it and fades after a few minutes in the air. The taste is savoury and rich, a bit like a very ripe cheese.

Ways to use it

• Cut into wedges, coat lightly in flour and deep fry, then serve with crisp fried holy basil and a chilli and garlic stir-fry, the dish known as khai yiao ma krapao krob.
• Make a spicy salad with sliced egg, shallot, chilli, Chinese celery, lime juice and fish sauce.
• Dice into rice porridge, jok, with a little ginger and spring onion.
• Serve sliced with pickled ginger and a few drops of soy sauce as a cold starter.

Use a thin knife or a piece of thread to cut it cleanly. The yolk is soft and sticks to a thick blade.

Storing it

Keep the eggs in a cool, dry place out of the sun, and go by the date on the pack. Once peeled, cover them and keep them in the fridge, then eat them within a day or two.

Where it comes from

Grown to certified organic standards. The certificate for each lot is shown when you trace your pack.

Every pack will carry a lot code. Enter it on the Trace your pack page and you will see the farms in that lot, the packing date and the certificate.