Using the back of a heavy spoon, make a series of cracks all over the eggshells, making sure the shell remains intact. (Don't worry if the shell does come off - it just means that egg will have a darker color than the others).
Congratulations on being the first person EVER (outside of my family) who knows what "Tea Eggs" are!
I can't believe it! I grew up on these eggs (as well as a similar preparation, "Anise Eggs."
What you should mention, is that the cook should peel these eggs before serving. The whites will have a crackled, spider-web looking design on them, and they will have a mild salt and tea flavor.
These eggs were favorites of all our guests at dinner parties.
I have since decided to make them for Halloween parties, and call them "Spider Eggs," to be festive, and a little gross for the children.
Another note, the Tea Eggs are not difficult to prepare. Don't be afraid to make a dozen or more at a time--eggs keep well, especially when boiled in brine and tea.