Trim and slice the flank steak thinly across the grain. Aim for even, thin strips but don't worry about perfection.

In a bowl combine the steak with 2 teaspoons oil, Shaoxing wine (or sherry), 1 teaspoon soy sauce, 1 tablespoon cornstarch, 1 tablespoon water, and 1/4 teaspoon baking soda. Toss until coated, then refrigerate for about 1 hour; add a splash of water if the meat seems dry.

Prep the sauce by dissolving 1/4 cup light brown sugar in 3/4 cup hot water or stock, then stir in 1/4 cup soy sauce and 1 teaspoon dark soy sauce if using. Set the mixture aside.

Spread the 1/2 cup cornstarch on a shallow plate or bowl and dredge each slice of marinated beef so it's evenly coated.

Heat 2/3 cup neutral oil in a wok or large skillet until it just starts to smoke. Working in batches, lay the beef in a single layer and sear about 1 minute per side until crisped. Remove each batch to a paper-towel-lined plate to drain.

Carefully discard most of the frying oil from the wok, leaving about 1 tablespoon. Increase the heat to medium-high and add the minced ginger and dried chilies; stir for roughly 15 seconds. Add the garlic and the white parts of the scallions and cook another 15 seconds, taking care not to burn the aromatics.

Pour the prepared sauce into the wok and bring it to a simmer. Mix the 1 1/2 tablespoons cornstarch with a small amount of cold water to form a slurry, then whisk it into the simmering sauce. Cook until the sauce thickens and becomes glossy.

Return the crisped beef and the green parts of the scallions to the wok. Toss everything together over high heat for about 30 seconds so the sauce clings to the beef and the scallions warm through.

Serve immediately with steamed rice, adjusting heat or sauce thickness as desired before plating.