In a medium bowl, combine the sliced flank steak with the baking soda, water and oyster sauce. Massage these ingredients into the beef until any liquid has been absorbed by the meat. Marinate for 30 minutes.
Lightly dredge all of the beef slices in cornstarch. Set aside until ready to fry.
Slice all the fresh peppers crosswise into thin slices on the diagonal. Set aside the dried red peppers. Do not break them open or chop unless you want a very spicy Hunan Beef!
Stir the sugar into 2 tablespoons of hot water until dissolved.
Add the Chinese black vinegar, soy sauce, and ground white pepper. Mix until well combined and set aside.
Heat your wok over high heat until smoking. Spread ⅓ cup oil around the wok, and sear the beef in three batches on both sides until browned and slightly crispy on the outside. Be sure the wok and oil are hot each time you add a batch of beef.
Drain the crispy beef by moving it up to the side of the wok. The oil will drain to the bottom and you can then transfer the beef to a sheet pan or plate. No need for paper towels or wire racks!
After frying the beef, leave about 2 tablespoons of the oil in the wok, and remove any excess. If your wok got burned in the frying process, this is a good time to wash it. While you want the beef flavor from frying, you definitely don’t want burned bits in the stir-fry if you got carried away with the heat during frying.