Prep the chicken: Pat the chicken dry with paper towels. Season lightly with salt and pepper.
Thin strips cook fast and stay tender.
Make the quick sauce: In a small bowl, whisk soy sauce, oyster/hoisin (if using), sesame oil, rice vinegar or lemon juice, honey, red pepper flakes, and broth. If you want a thicker glaze, stir in the cornstarch slurry.
Cook the broccoli: Heat a large skillet over medium-high. Add 1–2 teaspoons oil.
Toss in the broccoli and a pinch of salt. Stir-fry 3–4 minutes (a bit longer if using frozen) until bright green and crisp-tender. Transfer to a plate.
Sauté the aromatics: In the same pan, add the remaining oil.
Add onion and cook 2 minutes until slightly softened. Add garlic and cook 30 seconds until fragrant.
Cook the chicken: Add the chicken strips in a single layer. Let them sear for 2–3 minutes, then flip and cook another 2–3 minutes until just cooked through.
Avoid overcooking to keep them juicy.
Combine and sauce: Return the broccoli to the pan. Pour in the sauce. Toss everything together and simmer 1–2 minutes until the sauce slightly thickens and coats the chicken and broccoli.
Taste and finish: Adjust salt, pepper, and heat.
Sprinkle sesame seeds and green onions if you like. Serve as is, or spoon over cauliflower rice or a small portion of brown rice.