For The Marinade:

1. Combine the mirin, soy sauce, and water together and set aside. 

Cook The Eggs:

1. Fill a small 4 quart saucepan halfway with water. Bring to a simmer and add the white vinegar if using. Gently lower eggs into the pot, either with a slotted spoon or wire spider (try and do this in the fewest steps), which will cause the least amount of trauma to the eggs.
2. Set a timer and cook the eggs for 6 ½ minutes for a very liquid yolk, or 7 ½ minutes for a soft yolk.
3. Gently swirl the eggs with a spoon or chopsticks occasionally to center the egg yolk as it cooks.
4. In the meantime, get an ice bath ready for your cooked eggs. As soon as the timer rings, take the eggs out of the simmering water and transfer to the ice bath. Chill the eggs for a couple of minutes until completely cool.

Peel And Marinate:

1. Peel the eggs gently as the center is very loose and cannot handle rough handling. We use a light thin spoon to gently crack the eggs and then use the spoon to carefully pry the shell off, sliding the spoon under the membrane of the egg. Using a bowl of water and submerging the egg while peeling is often helpful.
2. Put the eggs in the smallest container that will fit them and pour the marinade over the eggs. You can also use a zip top bag, pressing out all of the air before sealing the bag. 
3. In order to keep the eggs submerged in the container, you can use a weight, like a small plate. Or take a piece of rinsed cheesecloth or even a paper towel and push down gently on the eggs so everything is soaked in the marinade.
4. Marinate the eggs overnight or at least 6 hours.
5. Use the eggs to top ramen, as a side dish, or a quick snack.