Slice 2 lbs of flank or sirloin steak against the grain into thin strips, about 1/4 inch thick.

In a mixing bowl, combine baking soda, cornstarch, kosher salt, vegetable oil, soy sauce, and mirin. Add the sliced beef and coat thoroughly. Cover and refrigerate for at least 1 hour.

In a separate bowl, whisk together oyster sauce, hoisin sauce, soy sauce, and brown sugar to prepare the sauce.

Heat 1/4 cup of vegetable oil in a wok over medium-high heat. Add marinated beef in batches, stir-frying for 2-3 minutes until caramelized.

Add minced garlic, grated ginger, white parts of green onions, and dried red chilies into the same pan. Sauté for about 30 seconds.

Pour the prepared sauce into the pan and let it simmer. Add the beef back to coat well and stir in the green onion tops.

Serve the Mongolian Beef over rice or noodles, garnished with green onions.