How to Make It
Preheat a grill to very high (500°F). Using a fork, prick eggplants all over. Place eggplants on oiled grates; grill, covered, turning occasionally, until skin is slightly charred and flesh is creamy and pulling away from skin, 15 to 20 minutes. Gently transfer to a rimmed baking sheet, and let cool 10 minutes.
Heat a small skillet over medium. Add Szechuan peppercorns and cumin seeds; cook, stirring often, until fragrant, about 2 minutes. Transfer to a spice grinder; add white peppercorns and cardamom seeds. Pulse until finely ground. Transfer to a medium bowl, and stir in gochugaru, 4 teaspoons salt, and 13-spice powder until combined.
Heat oil in a wok over medium-high until just smoking. Add dried chiles; cook 5 seconds. Add ground pork and 1/2 teaspoon salt; cook, breaking pork up with a spoon, until just cooked through and some bits of meat have begun to brown, about 1 minute and 30 seconds. Add scallions and fresh chiles, if using; cook, stirring constantly, until scallions are slightly wilted, about 15 seconds. Remove from heat, and stir in 2 teaspoons reserved spice mixture. (Reserve remaining spice mixture for another use.)
Place each roasted eggplant on its side. Slice into (but not through) each eggplant lengthwise, opening like a baked potato, making sure to leave shell of eggplant intact. Using a pair of kitchen scissors, cut up flesh of eggplants. Stir 1/4 teaspoon salt into the flesh of each eggplant. (Be careful not to loosen or incorporate the charred eggplant skin.) Spoon 2/3 cup pork mixture into each eggplant. Stir together eggplant flesh and pork mixture. Serve stuffed eggplants family style.