Beat the egg in a medium sized bowl. Add the sliced beef, vegetable oil, and salt. Mix well and let marinate for 15 to 20 minutes while preparing the other ingredients.
Mix the sauce
Combine everything for the sauce in a big bowl and mix well.
When you’re ready to cook, drain the extra liquid from the bowl of beef. Add the cornstarch. Stir to coat the beef, until it forms an uneven coating with a little dry cornstarch left unattached.
Heat oil in a large nonstick skillet (or a cast iron pan) over medium high heat until hot. Add the beef and spread into a single layer in the skillet. Separate the beef pieces with a pair of tongs or chopsticks.
Cook without touching the beef for 2 to 3 minutes, or until the bottom turns golden. Flip to brown the other side, 1 to 2 minutes. Transfer the beef to a big plate and remove the pan from the stove. Let cool for 2 to 3 minutes.
Place the pan back onto the stove and turn to medium heat. You should still have 1 to 2 tablespoons of oil in the pan. If not, add more.
Add the onion, pepper, and dried chili pepper. Cook and stir for 1 minute.
Add the ginger and garlic. Stir a few times to release the fragrance.
Stir the sauce again to dissolve the cornstarch completely. Pour into the pan. Stir and cook until it thickens a bit.
Add back the beef pieces. Stir to coat beef with sauce.
Transfer everything to a plate immediately and garnish with roasted sesame seeds, if using.
Serve hot over steamed rice as a main dish.
To make the dish gluten-free, use rice vinegar to replace Chinkiang vinegar, tamari or coconut aminos to replace soy sauce, and a gluten-free hot sauce such as Sriracha to replace the Doubanjiang.
Flank steak is my favorite cut for this dish, but you can use skirt steak, short ribs, or fajita meat, as well. If you decide to use a cheaper cut, such as as brisket or chuck roast, refer to my Orange Beef recipe to see how to tenderize the meat using baking soda.
You can use rice vinegar as an alternative, although the sauce will come out slightly different and less pungent.
Dark soy sauce will add a beautiful caramel color to the beef. You can use regular soy sauce as well but the dish will come out with a lighter color.
You can use other hot sauces such as Sriracha, sambal oelek, etc. The sauce will come out differently but still be tasty.