Slice the beef into thin pieces, about 1 inch wide and 2 inches long. In a bowl, combine the beef with the Shaoxing wine, salt, ginger and scallion. Let it marinate for approximately 30 minutes. After marinating, drain the beef and discard the ginger and scallion. Pat the meat dry with paper towels to avoid splattering during frying.
While the beef is marinating, soak the dried chenpi in warm water for about 30 minutes, or until softened. Drain the peels and cut them into thin strips; you should have about ⅓ cup. (If your chenpi has a thick pith, you can scrape some out with a spoon after soaking to remove some bitterness.)
Deseed the dried chilies and cut them into 3 pieces each.
Heat the oil in a wok to 300ºF (150ºC). Add the beef slices to the oil carefully, making sure they don’t splash. Fry the beef until it turns pale, about 1½ minutes, then remove it from the wok and set it aside on a plate lined with a paper towel to drain. You can fry the meat in batches if your pan is small.
Increase the oil temperature to 375ºF (190ºC). Return the beef to the oil and fry it again until it is browned and slightly crisp, about 2 minutes. Remove the meat from the pan again and drain it a second time on a paper towel-lined plate. Pour out the oil, reserving 2 tablespoons (filter and save the rest for reuse) and wipe the wok clean.
Return the 2 tablespoons of oil to the wok and heat it on low. Add the dried chilies and Sichuan peppercorns to the oil and stir-fry until they are fragrant and the chilies darken slightly. Add the sliced chenpi to the mix and stir everything until they are aromatic, about 1 minute, being careful not to burn the chilies.
Return the beef to the wok, add the chicken broth and bring the mixture to a gentle simmer over medium heat. Add the sugar and msg (if using), and continue simmering for 8–10 minutes or until the liquid reduces slightly and the beef looks glossy. Season with salt, if needed.
Turn off the heat and drizzle in the sesame oil; toss everything to coat. Serve this dish lukewarm or cold garnished with a sprinkle of sesame seeds and scallion greens.
