Shoyu Tamago, Japanese Soy Sauce Eggs
1. Place the desired number of eggs in a saucepan and fill the saucepan with cool water until the eggs are almost covered, but not quite. Put the saucepan on the stove and bring the water to a boil over medium heat. Let the eggs boil for 7 to 8 minutes (7 minutes for a softer yolk, and 8 minutes for a firmer yolk). Remove the saucepan from the heat and immediately run cold water over the eggs to stop them from continuing to cook. Peel the eggs carefully (I find that peeling them under cool running water helps).
2. Place the eggs in a plastic bag and add enough soy sauce so that they are covered. Press the air out of the bag and tie it shut. Put the bag in a bowl or container, in case the bag leaks, and put it in the refrigerator for an hour.
*If you want to make the eggs the night before, then you will need to dilute the soy sauce with water or dashi, otherwise the eggs will become unpleasantly pungent. I find that a ratio of 1:1 or 2:1 (1 or 2 parts water or dashi to 1 part soy sauce) keeps the eggs from becoming too strong. If you want to make a larger batch of eggs to use over several days, then the same is true. Using a ratio of 3:1 or 4:1 (3 or 4 parts water or dashi to 1 part soy sauce) will keep the eggs from becoming too strong and is good for about 3 days.