Step 1: Prepare the Beef

• Slice the flank steak thinly against the grain into bite-sized pieces. This ensures the beef remains tender.
• Toss the beef slices in cornstarch, coating each piece evenly. Set aside for 10 minutes to allow the cornstarch to adhere.

Step 2: Make the Sauce

• In a small bowl, whisk together soy sauce, brown sugar, water, cornstarch, sesame oil, minced ginger, and garlic. Set aside.

Step 3: Sear the Beef

• Heat the vegetable oil in a large skillet or wok over medium-high heat.
• Add the cornstarch-coated beef in a single layer, cooking for 2-3 minutes on each side until browned and crispy. Cook in batches if necessary to avoid overcrowding the pan.
• Remove the beef from the skillet and set it aside on a plate lined with paper towels.

Step 4: Cook the Sauce

• Drain excess oil from the skillet, leaving about 1 tablespoon.
• Pour the prepared sauce into the skillet and bring it to a simmer over medium heat, stirring frequently.
• Add the green onions (if using) and cook for 1-2 minutes until they soften slightly.

Step 5: Combine Beef and Sauce

• Return the cooked beef to the skillet and toss to coat evenly in the sauce. Simmer for 2-3 minutes, allowing the sauce to thicken and the beef to absorb the flavors.

Step 6: Serve

• Remove from heat and serve immediately over steamed rice or noodles. Garnish with additional green onions or sesame seeds if desired.