Heat 2 Tbsp oil in a large pan over medium-high heat until very hot. Add the eggplant pieces and cook, stirring periodically, until eggplant is soft and turning golden brown, about 10 minutes. Remove eggplant from pan and set aside.
Add the remaining Tbsp of oil to the hot pan, and once heated, add the scallion, garlic, and ginger. Cook, stirring often, until soft and fragrant, about 2-3 minutes.
Add the ground pork, and cook, breaking pork into small pieces, until it is completely browned and cooked through.
Stir together the doubanjiang, soy sauce, and 1/4 cup water and add it to the pan with the pork and cook for 1-2 minutes.
Combine the cornstarch with 2 Tbsp water, the add this to the pan, stirring until sauce begins to thicken slightly, about 1-2 minutes more. Stir in the eggplant until it is well mixed and well coated with the sauce. Garnish with sliced scallions and serve atop rice.