Pat the steak dry with paper towels. Slice thinly against the grain into 1/8–1/4-inch strips. In a bowl combine 3 tbs soy sauce, 1 tbs Shaoxing wine, 1 tsp cornstarch, 1 tsp sesame oil, and 1 tsp freshly ground black pepper. Add the sliced steak, toss to coat thoroughly, cover, and refrigerate for 15–30 minutes to tenderize and season.

Vegetables & Aromatics

Prepare vegetables

While the steak marinates, seed and slice bell peppers into 1/2-inch strips and cut the onion into 1/2-inch wedges. Mince the garlic and ginger finely. Slice scallions thinly and set aside for garnish.

Sauce

Mix sauce

In a small bowl combine 3 tbs beef broth, 1 tbs oyster sauce, 1 tsp dark soy sauce (optional), and 1 tsp brown sugar. In a separate small bowl, whisk 1 tsp cornstarch with 2 tbs cold water to make a smooth slurry. Set both aside.

Stir-fry & Finish

Heat wok and sear steak

Heat a large wok or heavy skillet over high heat until very hot. Add 1 tbs neutral oil and swirl. Add marinated steak in a single layer (work in batches if necessary to avoid crowding). Stir-fry 1–2 minutes until the edges brown but the interior is still slightly pink. Remove seared steak to a plate and keep warm.

Cook vegetables

Add the remaining 1 tbs oil to the wok. Add the onion and stir-fry 30–45 seconds until it starts to soften. Add the bell pepper strips and continue stir-frying 1–2 minutes until peppers are crisp-tender. Push vegetables to the side.

Aromatics

Add the minced garlic and ginger to the empty center of the wok and stir-fry 10–15 seconds until fragrant, taking care not to burn them. Then toss garlic and ginger with the vegetables.

Combine steak and sauce

Return the seared steak and any accumulated juices to the wok. Pour the prepared sauce over the mixture and stir to combine. Bring to a gentle simmer for about 30 seconds.

Thicken sauce

Give the cornstarch slurry a quick stir and pour it into the wok while stirring constantly. Cook 30–60 seconds until the sauce thickens and becomes glossy, coating the steak and vegetables.

Season and finish

Taste and season with up to 1/4 tsp salt and additional freshly ground black pepper to taste. Remove from heat and garnish with sliced scallions if using.