Japanese cuisine is full of little surprises that turn an average dish into a spectacular, put-a-smile-on-your-face delight. The sweet chicken heart you sometimes find on your yakitori skewer, the explosion of color that pops out of the bento box, and the perfectly cooked yolk from the marinated soft-boiled egg used in traditional ramen soups all take their respective dishes from great to how-cool-is-that great. "Ajitsuke tamago" -- the eggs used in ramen -- roughly translates to "seasoned egg that is soft-boiled," and that's pretty much all they are. Like most things Japanese food, ajitsuke tamago are simple, elegant and easy to make.
Make a marinade to season the eggs with. One part each mirin, soy sauce and sugar to two parts each sake and cold water comprise a traditional ajitsuke tamago marinade, using ingredients you can get at just about any store. You can add your own aromatic ingredients, such as shredded ginger, sesame oil and dashi, a type of Japanese fish stock, to taste. Set the marinade aside.
Pour 3 quarts of cold water in a heavy-bottomed saucepan for one to six eggs and bring it to a simmer on the stove. Use 6 quarts of water for seven to 12 eggs. You need around 3 quarts of water for every half-dozen eggs so the temperature doesn't drop significantly when you lower the eggs into it.
Lower the heat when the water starts to simmer so it barely quivers. Lower the eggs in the water with a slotted spoon. Always start soft-boiled eggs in simmering water to prevent the yolks from cooking at the same rate as the whites. When you start eggs in simmering water, the yolks stay fluid while the whites set.
Simmer the eggs for five minutes and 45 seconds to six minutes and remove the eggs with a slotted spoon. Tap the broad side of each egg while still warm on a flat surface to crack the shell. Roll the egg forward and backward under your palm until cracks form all over, then grab the shell and peel it off. Don't tap the eggs on an edge, or pieces of shell will stick in the white.
Place the eggs in a food-storage container and pour marinade over the eggs until just the very tops of them pop out of the surface. Fold a few paper towels into a square and place them over the eggs, allowing them to soak up the marinade. The paper towels keep the tops of the eggs in contact with marinade.
Marinate the eggs in the refrigerator for four to 12 hours. Place the eggs in the hot ramen when ready and cut them open with a spoon to let the flavorful fun begin.
Attach a candy thermometer to the saucepan and adjust the heat as needed so the water maintains a constant temperature of 180 degrees Fahrenheit if you want to be precise about boiling soft-boiled eggs. Don't use fresh eggs for soft-boiling. Fresh eggs have a white inner-shell membrane that sticks to the white. Eggs at least five days old work best.
The U.S. Department of Agriculture recommends cooking eggs until the yolks are firm. Don't marinate the eggs longer than 12 hours, or they will toughen as if overcooked. Discard the marinade after use.