In a small saucepan, combine the stock, preserves, tamari and ginger. Bring the plum sauce to a simmer, stirring occasionally, over medium.
In a large skillet, heat the oil, two turns of the pan, over high. Add the pork and cook, stirring and breaking up with a wooden spoon, until browned. Season with the five-spice powder, then add the scallions, chiles and garlic; season with the Szechuan pepper. Stir-fry until the scallions soften, about 2 minutes. Add the plum sauce and stir-fry until the sauce is absorbed, 1 to 3 minutes. Transfer to a serving dish, drizzle with the sesame oil and top with the peanuts, sesame seeds and herbs. Serve with the lettuce leaves for wrapping.