Start by thinly slicing your flank steak against the grain. Gather all other ingredients, including soy sauce, ginger, garlic, and brown sugar.

Toss the sliced flank steak with cornstarch in a large bowl until evenly coated. Let sit for 5 minutes.

Heat vegetable oil in a large skillet over medium-high heat. Add the coated beef in batches and cook for 2-3 minutes until golden brown and crispy.

In the same skillet, sauté minced ginger and garlic for about 30 seconds until fragrant, then add soy sauce and brown sugar. Stir for 1-2 minutes until the sugar dissolves.

Return the crispy beef to the skillet, tossing it in the sauce. Cook for an additional 1-2 minutes until well coated.

Serve hot over steamed rice, optionally adding stir-fried vegetables.