Directions

1. Cut steak with the grain into 2-inch-wide pieces. Cut each piece across the grain into 1/4-inch-thick slices. In a large bowl, toss steak, 1 Tbsp. cornstarch, 2 tsp. soy sauce, 1 tsp. brown sugar, and 1 tsp. sesame oil together until well coated. Marinate at room temperature for about 20 minutes.
2. In a medium bowl, whisk together remaining 1/3 cup soy sauce, the broth, remaining 1 Tbsp. cornstarch and 1 Tbsp. brown sugar, the rice vinegar, sherry, sriracha, ginger, remaining 1 tsp. sesame oil, the garlic, and 1/4 tsp. pepper. Set sauce aside.
3. Heat oil in a wok or large saute pan over high heat. Add steak in a single layer (if needed, cook half at a time so it isn’t crowded) and cook undisturbed until well browned, about 2 minutes. Turn with a wide spatula and cook the other side until browned, about 2 minutes more. Transfer to a plate.
4. Reduce heat to medium-high and add onion. Cook, stirring occasionally, for 1 minute. Add broccoli and water, cover pan, and cook until broccoli is bright green, about 2 minutes. Stir in bell pepper and cook, covered, until it’s just beginning to soften, 1 minute more. Remove lid and let liquid cook off.
5. Return beef to pan and pour in sauce. Cook, stirring often, until sauce thickens, 1-2 minutes. Season with more pepper to taste if you like. Stir in half of scallions and sprinkle the rest on top. Serve over steamed rice.