Ajitsuke Tamago

Bring a pot of water to a vigorous, rolling boil — enough water to cover the eggs by at least 2 cm. Lower the eggs in one at a time using a slotted spoon or spider, straight from the refrigerator (cold eggs into boiling water give more predictable timing). Boil at a steady medium-high simmer — not a furious churn that cracks the shells — for exactly 6 minutes and 30 seconds. Meanwhile, prepare an ice bath in a large bowl. At time, transfer immediately to the ice bath and chill for at least 5 minutes before peeling.

Peel the chilled eggs under a thin stream of cold running water. Crack the shell all over by rolling the egg gently on the counter, then begin peeling from the broad end where the air pocket is, slipping your thumb under the membrane. The cold water helps the membrane separate from the white cleanly. Work slowly — a 6.5-minute egg white is set but more delicate than a hard-boiled one. Pat dry with kitchen paper when done.

Combine the soy sauce, mirin, sake, water, and kombu in a small saucepan. Bring to a gentle simmer over medium heat and cook for 3 minutes to cook off the alcohol from the sake and let the kombu begin releasing its glutamates. Remove the kombu after 4 minutes total (over-steeped kombu turns slimy and bitter). Cool the tare completely to room temperature before adding the eggs — adding warm eggs to warm tare cooks the yolk further. The tare can be prepared hours ahead.

Place the peeled eggs in a zip-lock bag or a snug container just large enough to hold them. Pour the cooled tare over the eggs and seal the bag, pressing out the air so the tare contacts every surface of each egg. Refrigerate for at least 4 hours; overnight (8–12 hours) is ideal. Do not exceed 24 hours — the salt will tighten the white to a rubbery, overly-dense texture and the yolk will lose its fudginess. Turn the bag occasionally so all sides marinate evenly.