You may have had tea/soy eggs on ramen or as a street food in some parts of Asia. Tea Eggs and Soy Eggs are not exactly the same but the technique of boiling followed by marinating, as well as most of the ingredients, are the same so I thought I'd put them together. For Soy Eggs just leave the black tea out of the recipe.
Often the eggs are beautifully marbled - that is achieved by leaving the eggs in their cracked shells while they marinate - but I have had mixed results with that and they are just as tasty (maybe more so), if not as beautiful, if you marinate them without their shells.
They take a bit of time to make but last well in the fridge so you can make a batch and pull them out over the course of the week.
"Jammy Eggs" are those beautiful boiled eggs that have solid hard-boiled whites and slightly loose, or jammy, yolks. We like them on toast, on top of a rice bowl or with a salad - whether they've had a bath in a marinade or not. And they are super easy to make.
Add all marinade ingredients to a pan, bring it to a boil and then turn it down to a simmer for 10 minutes. Take off the heat and let cool to room temperature. Strain out the spices and the tea.
While the marinade is cooling, bring a pot of water that is enough to cover your eggs to a boil and gently add the refrigerated eggs*. Set a timer for 6 minutes and 50 seconds (I know, right!?) and cook the eggs at a simmer. While the eggs are simmering, make an ice bath in another bowl or pot - just cold water and 6-12 ice cubes. Once the timer goes off, lift each egg out of the hot water and into the ice bath to stop the cooking process - don't skip this or your eggs will be over-cooked.
Peel the eggs gently (remember, they are not as firm as hard boiled eggs) under the water and when they are all peeled, drain the water.
Put the eggs in a container that just holds the eggs (too big and the marinade won't cover them). Pour the marinade over the cooked eggs and refrigerate for at least 4 hours. Store in the marinade unless they are becoming too salty for you, in which case store them in separate container in the fridge.
Adapted from: https://omnivorescookbook.com/chinese-tea-eggs/