In a large bowl, mix soy sauce, mirin, and dashi stock or water.
To prepare the eggs, add 3 tbsp of vinegar to a pot of water, bring it to a simmer.
Once the water is simmering (not boiling), gently add in the eggs, set the timer to 7 minutes for the perfect yolky egg. If you prefer your egg yolks more cooked, cook them for another 1-2 minutes.
After 7 minutes, add the eggs into an ice bath and let them rest for at least 3 minutes.
To help the peeling process, crack the front and back of the eggshell using a pointy teaspoon. Using the tip, slide the teaspoon into the layer between the egg and the shell, and peel off the shell.
Add the eggs into the marinade and let it rest for at least 3 hours or overnight.
