This clever use of fresh cabbage and leftover boiled corned beef is inspired by Chinese American-style kung pao chicken. It gets fiery heat from chiles, tingling spice from Sichuan peppercorns and delightful crunch from roasted peanuts.
Mix the scallion whites, ginger, garlic and Sichuan peppercorns (if using) together in a small bowl. Whisk the hoisin sauce, soy sauce, sherry, vinegar and cornstarch together in another small bowl.
Heat a very large cast-iron skillet or wok over high heat. Add the oil and swirl to coat the pan. Add the chiles and stir-fry until they blister and deepen in color, 5 to 10 seconds. Transfer the chiles to a large bowl with a slotted spoon. Add the corned beef and stir-fry until lightly browned and heated through, 2 to 3 minutes; transfer the beef to the bowl with the chiles.
Add the cabbage and scallion mixture to the skillet and stir-fry until the cabbage starts to soften around the edges, 2 to 3 minutes. Return the corned beef and chiles to the skillet. Add the hoisin sauce mixture and stir-fry until hot, about 1 minute. Stir in the peanuts and scallion greens. Transfer to a serving platter. Serve right away with steamed rice.