In a large bowl, mix the pork with the vinegar, sambal, cornstarch and 1 Tsp of the soy sauce. Cover and refrigerate for at least 2 hours or up to 8 hours. Preheat a grill and position the rack 8 inches from the heat. Brush the eggplants with peanut oil and season with salt. Arrange the eggplants cut side down on a rimmed baking sheet and broil for 12 to 15 minutes, turning once, until lightly charred and tender.
Meanwhile, in a medium bowl, whisk the chicken stock with the sake, sugar, sesame oil, chilli bean paste and remaining soy sauce.
In a wok heat some peanut oil until shimmering. Add the minced scallions, garlic and ginger and stir-fry over high heat until fragrant, 1 minute. Add the pork and stir-fry until no pink remains. Add the chicken stock mixture and bring to a boil. Simmer over moderately high heat, stirring occasionally, until slightly thickened, about 3 minutes.
Arrange the eggplants cut side up on a platter and spoon the pork on top. Garnish with thinly sliced scallions and serve with steamed rice.