Prep the beef: Freeze the steak for 15–20 minutes to firm it up. Slice thinly against the grain, about 1/8 to 1/4 inch thick. Pat dry with paper towels so it crisps better.

Mix the sauce: In a bowl, whisk soy sauce, oyster sauce, brown sugar, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes. In a separate cup, stir cornstarch and water until smooth, then whisk into the sauce.

Marinate briefly: Toss the sliced beef with half of the sauce. Set aside for 10–15 minutes while you prep the broccoli. Reserve the other half of the sauce for finishing.

Prep the broccoli: Cut florets into small, even pieces. Toss with 1 teaspoon of the neutral oil and a pinch of salt.

Preheat the air fryer: Heat to 390–400°F (200–205°C) for 3–5 minutes. Lightly oil the basket or use a parchment air fryer liner if you like.

Cook the beef in batches: Shake excess marinade off the beef. Spread in a single layer with space between slices. Air fry for 4–6 minutes, flipping halfway, until browned at the edges and just cooked through. Transfer to a bowl and tent loosely with foil. Repeat with remaining beef.

Cook the broccoli: Add broccoli to the basket in a single layer. Air fry at 380°F (193°C) for 5–7 minutes, shaking halfway, until crisp-tender with charred spots. If you like softer broccoli, cook 1–2 minutes longer.

Thicken the sauce: Pour the reserved sauce into a small skillet or saucepan. Simmer over medium heat for 1–2 minutes until glossy and slightly thick. If needed, add a splash of water to loosen.

Toss to finish: Add beef and broccoli to a large bowl. Pour the thickened sauce over and toss to coat. Taste and add a pinch of salt or a squeeze of lime if needed.

Serve: Spoon over hot rice or noodles. Garnish with sesame seeds and green onions.