Bring water to a boil in a steamer. Cut the eggplant in half horizontally and vertically, place in a bowl and carefully place bowl into steamer when water begins to boil. Steam for about 20 minutes. You want the eggplant to be luxuriously soft and creamy. Remove from steamer and let cool, then cut each piece into bite-size pieces.Instant Pot instructions: Place steamer trivet in bottom of pot and place bowl of eggplant (prepped as above) on trivet, making sure steam can circulate around it. Cook on Steam setting for 12 minutes with natural release of 5 minutes.
While eggplant is steaming, roast the green chilies. This can be done directly over a stovetop fire, in a hot, dry pan or under a broiler. Turn the chilies so that all of the skin gets charred and the chili blackens almost entirely, as larger chilies will need to cook that long to be roasted. Put blackened chilies in a plastic bag and let them sweat for a few minutes so the skin will be easier to remove. When cool, peel the skin off, remove the seeds and mince the chilies finely.
In a bowl or large mixing cup add the garlic and vinegar and let the garlic soak for a few minutes to tame the heat. Then add the other sauce ingredients: oil, soy sauce, Sichuan pepper oil, oyster sauce, Maggi seasoning, chili oil and sugar. Whisk ingredients together until well blended and emulsified. Add minced green chilies to the sauce.
Arrange room-temp eggplant pieces in a shallow serving bowl and pour the green chili sauce over them. Garnish with green onion. Serve at room temperature.