Fry the Onions (The Flavor Engine)
Toss the sliced onions with the cornstarch and salt in a large bowl until evenly coated. Heat the neutral oil in a large, deep skillet or Dutch oven over medium heat. Fry the onions in batches, stirring frequently, until they turn a deep golden-brown color. Remove with a slotted spoon and spread them out across a paper-towel-lined baking sheet. Reserve all the remaining cooking oil.
This step creates the ultra-crisp signature topping and produces a deeply aromatic onion oil that flavors every other component of the dish.
Onions should be deeply golden, turning rigid and loudly crunchy as they cool.