Cantonese: Cha Yip Dan
Mandarin:Cha Ye Dan
Hard-boiled eggs are tough and dry but they become softer after they have been cooked in tea (tea egg). Another thing is tea eggs can stay longer, so they are good snacks for mountaineers in the old days.
Marble tea egg solution: it is a mixture of water, black tea leaves, soy sauce, sugar, cracked peppercorns, strips mandarin peel, and cinnamon stick.
Repeat with all the eggs. Make sure none of the eggshells is removed. Bring the tea egg solution to a boil. Place the eggs in the mixture, cover the lid of the pot and lower the heat to simmer. Boil the eggs for an hour before serving.
Children of the old days were given boiled red eggs from moms on their birthdays.
Simple. There were red incense papers for village rituals. Moms would wet one and cover a hot boil egg with it for half an hour. Remove the red cover paper and there you go, a red egg for birthdays!