Select one pound beef flank steak and locate the visible grain running in one direction across the meat.

Slice the beef against the grain perpendicular to the fiber direction into strips approximately one-quarter inch thick and two to three inches long.

Transfer sliced beef to a bowl and sprinkle one-half teaspoon baking soda over all strips tossing gently to coat every piece.

Allow beef to sit at room temperature for exactly fifteen minutes during which the alkaline environment weakens myosin-actin bonds and creates microscopic pockets for water retention.

After exactly fifteen minutes rinse the beef thoroughly under cold running water stirring gently to remove all residual baking soda residue.

Pat beef completely dry with paper towels spending thirty seconds removing all surface moisture that would create steam during searing.

Combine one-half cup fermented soy sauce one-half cup low-sodium stock one tablespoon brown sugar one tablespoon rice vinegar and one tablespoon minced fresh ginger in small bowl whisking until brown sugar dissolves.

Place large heavy-bottomed skillet over high heat for two to three minutes until the surface reaches approximately three hundred seventy-five to four hundred degrees Fahrenheit.

Add one and one-half tablespoons oil to the screaming-hot skillet swirling to coat the entire bottom evenly.

Add velveted beef strips to hot oil in single uncrowded layer allowing them to sit undisturbed for forty-five to sixty seconds on first side creating caramelized exterior.

Flip beef strips using tongs and sear second side for thirty to forty-five seconds until dark caramelized color develops on both sides.

Remove seared beef to clean plate and if you have more than three-quarter pound beef work in a second batch adding additional oil and repeating the searing process.

Add remaining one and one-half tablespoons oil to skillet and allow to heat for fifteen seconds.

Add three cups fresh broccoli florets in single uncrowded layer allowing them to sit undisturbed for sixty to ninety seconds then tossing gently and cooking another ninety to one hundred twenty seconds until tender-crisp with light browning.

Return seared beef to skillet along with prepared sauce base bringing mixture to rapid boil.

Whisk one and one-half tablespoons cornstarch with one-quarter cup cold water in small cup until completely smooth creating the slurry.

Pour cornstarch slurry into boiling sauce while stirring constantly for approximately thirty seconds until sauce thickens and clings to all ingredients creating glossy unified suspension.

Add four cloves minced fresh garlic during final ten to fifteen seconds stirring briefly then removing from heat immediately.

Drizzle one tablespoon toasted sesame oil over beef and broccoli for finishing richness and aromatic depth.

Sprinkle one-quarter teaspoon optional red pepper flakes if desired.

Plate immediately and garnish with one-quarter cup fresh sliced scallions scattered across the top.