01 - Combine sliced flank steak with soy sauce, Shaoxing wine, and cornstarch in a small bowl. Mix thoroughly to coat and let stand for 10 minutes to tenderize.
02 - Blanch green beans in boiling water for 2 minutes until bright green and crisp-tender. Drain immediately and rinse under cold water to stop cooking process.
03 - Heat 1 tbsp vegetable oil in a large wok over high heat until smoking. Add marinated beef in a single layer and stir-fry for 2-3 minutes until browned on edges but still pink inside. Remove beef and set aside.
04 - Add remaining 1 tbsp oil to the wok. Add Szechuan peppercorns and dried red chilies, stir-frying for 30 seconds until fragrant and toasted, taking care not to burn.
05 - Add minced garlic, ginger, and half the scallions to the wok. Stir-fry for 30 seconds until aromatic and just beginning to color.
06 - Add blanched green beans to the wok. Stir-fry for 2-3 minutes over high heat until skins begin to blister and develop charred spots.
07 - Return beef to the wok along with chili bean paste, both soy sauces, black vinegar, sugar, and sesame oil. Toss everything vigorously for 1-2 minutes until well coated and heated through.
08 - Transfer to a serving platter and garnish with reserved scallions. Serve immediately while steaming hot, accompanied by steamed jasmine rice.