Velvet the Beef: Place the thinly sliced flank steak in a medium bowl. Add 1 Tbsp soy sauce, rice wine, baking soda, 1 Tbsp vegetable oil, and 1.5 Tbsp cornstarch. Use your hands to massage the mixture into the beef thoroughly. Let the beef marinate at room temperature while you prepare the remaining ingredients, about 10-15 minutes. This step is essential for that signature tender beef texture in your Pepper Steak Stir Fry.

Prepare the Sauce: In a separate small bowl, whisk together the beef broth, 3 Tbsp soy sauce, oyster sauce, brown sugar, hoisin sauce (if using), and black pepper. Set this aside. In a third, very small bowl, mix the cornstarch and water to create your thickening slurry. Keep it near the stove.

Sear the Beef: Heat 2 tablespoons of oil in a large wok or high-sided skillet over medium-high to high heat, until shimmering. Add the marinated beef in a single layer, ensuring not to crowd the pan, which would lower the temperature. Sear the beef for about 60 to 90 seconds per side until beautifully browned but still slightly pink inside. You may need to do this in 2 batches to ensure the wok stays hot. Remove the seared beef with a slotted spoon and set it aside in a clean bowl.

Stir Fry the Aromatics: Reduce the heat slightly if needed and add another teaspoon of oil to the wok. Add the minced garlic and ginger. Stir continually for about 30 seconds until incredibly fragrant. Do not burn them, or the entire dish will taste bitter.

Cook the Vegetables: Add the sliced onions and bell peppers to the wok. Stir-fry aggressively for 3-5 minutes. We want the vegetables to be tender-crisp, releasing their moisture and sweetness but retaining a nice snap. This texture contrast is vital to a great Sizzling Chinese Pepper Steak with Onions.

Combine and Thicken: Return the seared, reserved beef to the wok along with the vegetables. Give the prepared sauce mixture a quick whisk and pour it over the beef and vegetables. Bring the sauce to a rapid simmer.

Create the Gloss: Stir the cornstarch slurry once more and pour it slowly into the simmering sauce, stirring constantly. The sauce will rapidly thicken and become glossy, enveloping all the ingredients in a beautiful, rich coat. Stir for about 30 seconds until the sauce has reached the desired consistency.

Finish and Serve: Turn off the heat and stir in the sesame oil. Taste and adjust seasoning, adding a little more soy sauce if needed. Transfer the Pepper Steak with Onions immediately to a serving platter. Garnish with green onions or sesame seeds if desired. Serve hot over steamed rice.