In a mixing bowl, combine thinly sliced flank steak or sirloin with 1 tablespoon of soy sauce, 2 teaspoons of cornstarch, and 1 tablespoon of vegetable oil. Stir well and let it marinate for about 10 minutes.

Heat a large wok over high heat until it's smoking hot, approximately 2-3 minutes. Add 2 tablespoons of vegetable oil and swirl to coat the wok. Carefully add the marinated beef in a single layer, searing for about 2 minutes until it turns opaque but still slightly pink in the center. Remove the beef and set aside.

Reduce the heat to medium and add more vegetable oil if needed. Toss in minced ginger and stir-fry for about 1 minute until fragrant. Add sliced garlic, 2 tablespoons of Sha Cha sauce, and 2 teaspoons of sugar. Cook for another 2 minutes until aromatic and begins to bubble.

Return the seared beef to the wok with the cut scallions. Increase heat back to high and stir-fry for about 1 minute until scallions wilt and flavors meld beautifully.

Transfer the completed Sha Cha Beef Stir-fry onto a serving plate or over a bed of steamed white rice and serve immediately while hot.