Cut the stem end off the eggplant, but don't trim the blunt end. Cut the aubergine in half lengthways, then cut each piece across once so as to make four quarters of roughly the same size - you should cut much nearer the blunt end. Bear in mind that the stem ends seem to lose more size in cooking.
In a pan wide enough to take all four pieces in a single layer, bring 750 milliliters / 1.6 pints water to the boil. Add the eggplants, skin side down, and reduce the heat. Simmer for about 5 minutes, turning after about 3 minutes, until soft but not mushy (test by pricking with a fork).
Drain the eggplant pieces and cool on a plate, skin side up (don't throw away the remaining liquid; use it to make stock). More liquid will come out as they cool; when cool enough to handle, press gently with your hand to squeeze out water without crushing the eggplant. Avoid squeezing out too much - the eggplant should still be somewhat moist.
When cool, slice each piece lengthwise into 3 milliliter / 1/8 inch pieces. Arrange slices casually on small dishes or saucers. Mix ginger and soy sauce and spread on top of the aubergine.
The original recipe used 10 x 10 centimeter (4 x 4 inch) eggplants, halved lengthways, but I can usually only find bigger ones. The author recommends using kikkoman soy sauce for all her recipes; and I agree with her. It's easier to grate the ginger if it's frozen; and this is also the best way to keep it fresh (it doesn't lose its flavour, as frozen garlic can).
This dish can be served hot, at room temperature, or chilled. To serve hot, slice and dress the eggplant as soon as it's cooled enough for you to handle.