Salted duck eggs are normally boiled or steamed before being peeled and eaten as a condiment to congee or cooked with other foods as a flavouring. The egg white has a sharp, salty taste. The orange red yolk is rich, fatty, and less salty. The yolk is prized and is used in Chinese mooncakes to symbolize the moon.
Despite its name, salted duck eggs can also be made from chicken eggs though the taste and texture will be somewhat different, and the egg yolk will be less rich.
Salted eggs are also popular in the Philippines. Salted eggs sold in the Philippines undergo a process of curing similar to that described above, with some variation in ingredients used. It is sold over the counter pre-cooked and ready to eat. The commercial salted eggs are duck eggs, and are dyed entirely red to make them look more distinctive, as they are also packaged, transported, and displayed in egg trays similar to those used for fresh eggs.
A popular method for processing salted eggs in the Philippines is the Pateros method. The salted egg is prepared Pateros style by mixing clay (from ant hills or termite mounds), table salt and water in the ratio of 1:1:2 until the texture of the admixture becomes smooth and forms a thick texture similar to cake batter. The fresh eggs are individually dipped in the admixture, and packed in 150-egg batches in newspaper-lined 10x12x18 inch wooden boxes (often residual boxes of dried fish packing). The whole batch is then lightly wrapped in newspapers to slow down the dehydration process.
The eggs are then stored indoors at room temperature over the next 12 to 14 days to cure. This way the salt works its way into the eggs uniformly in the batch. Curing can last up to 18 days, but that results in very long-lasting red eggs that can have a 40-day shelf life, which is largely unnecessary, as the eggs are stocked and replenished biweekly.
After the two-week curing period, the eggs are hand-cleaned with water and a brush and prepared to be boiled in low heat for 30 minutes. Time is measured from the first moment the water boils and the immersion of the eggs. The 50-egg batch is then wrapped in fish nets for ease of removal from the cookware. The cookware must be large enough to accommodate the batch with a two-inch covering of water.
Chicken eggs may be processed the same way, although, up to 10% of the batch can break during the process.