Prep everything first: slice beef across the grain into bite-sized strips (if not pre-cut), wash and cut vegetables into uniform pieces (small florets for broccoli, thin strips for pepper, matchsticks for carrot), mince the garlic and grate the ginger, and portion out the rice. Doing all mise en place ensures the fast, high-heat cooking step goes smoothly—stir-fries cook quickly and you won’t have time to chop once the pan is hot.

Marinate the beef: in a bowl combine 1 tbsp soy sauce (half of the total), 1/2 tsp cornstarch, a generous pinch of freshly ground black pepper and 1/8 tsp salt. Toss the beef to coat and let sit 8–10 minutes while you prep the pan. The light cornstarch coating protects the surface of the beef from drying, helps the meat brown evenly and gives the final sauce a silky sheen.

Warm the cooked brown rice (if using refrigerated rice): spread on a plate and microwave for 1–2 minutes covered or warm gently in a skillet with a splash of water. Day-old (chilled) rice separates more easily for serving and will not clump — it gives the best texture against the saucy stir-fry.

Heat a wok or large heavy skillet over high heat until very hot (you should see faint wisps of smoke). Add the neutral oil and swirl to coat. A very hot pan sears the beef quickly, producing Maillard browning (those flavorful browned bits) and locking in juices—don’t crowd the pan or the beef will steam instead of sear.

Sear the beef in a single layer, in a couple of quick batches if necessary: lay the strips in the hot oil, leave undisturbed for 30–45 seconds to form a crust, then stir and cook until just browned but still slightly underdone (about 1–1.5 minutes total). Remove beef to a plate. Undercooking slightly is intentional since it will finish cooking later and prevents overcooking lean strips.

Stir-fry the vegetables: if your broccoli is firm, add the florets first and toss for 1 minute, then add bell pepper and carrots and continue to stir-fry 2–3 minutes until the vegetables are bright, slightly blistered on edges and tender-crisp. High heat and quick cooking preserve color, crunch and nutrients—you want the vegetables lively, not mushy.

Add aromatics: push the vegetables to the side, add a touch more oil if the pan is dry, then add the minced garlic and grated ginger and stir 20–30 seconds—just until fragrant. Garlic and ginger burn quickly; adding them late prevents bitterness and keeps them bright.

Make the sauce and finish: in a small bowl whisk together the remaining 1 tbsp soy sauce, the toasted sesame oil (1 tbsp), 1/2 tsp sugar, 2 tbsp water, and the remaining 1/2 tsp cornstarch dissolved in 1 tbsp water (slurry). Pour the sauce into the pan, stirring to combine—the cornstarch slurry will thicken rapidly, coating the vegetables with a glossy sauce. Return the beef and any accumulated juices to the pan and toss for 30–60 seconds until the beef is cooked through and everything is well glazed.

Taste and adjust: quickly taste a small piece and adjust seasoning with a pinch of salt or a splash more soy if needed. Remember soy is salty—adjust lightly. Finishing with a few turns of freshly ground black pepper brightens the whole dish.

Serve: divide the warm brown rice between two bowls or plates, top with the beef and vegetables, sprinkle with sliced scallions and toasted sesame seeds if using. Serve immediately while the textures are still crisp-tender and the rice warm.