Begin by thinly slicing the skirt steak against the grain for optimal tenderness. In a bowl, toss the beef slices with cornstarch until evenly coated.

In a large skillet, heat 2 tablespoons of vegetable oil over medium heat until shimmering. Add the sliced white onions and sauté until translucent.

Stir in the julienned carrots and continue cooking until they soften slightly.

Add minced garlic, grated fresh ginger, and dried red chili flakes to the skillet. Cook all ingredients until fragrant.

In a separate bowl, whisk together light soy sauce, vinegar, sesame oil, black pepper, and brown sugar. Pour this mixture into the skillet.

Heat enough vegetable oil in another skillet to cover the bottom. Add the coated beef slices and fry until golden brown and crispy.

Drain the beef on paper towels and toss in the skillet with the prepared sauce.

Garnish with toasted sesame seeds and chopped green onions. Serve immediately while hot.