Wok hei is that smoky, charred quality that defines great Cantonese stir fry. It comes from a screaming-hot wok flashed with oil at the right moment, and a home stove will never put out the BTUs of a restaurant burner. But you can still get a beautifully blistered char on your beef and broccoli if you prep like a pro.
Prep matters more than power. Everything has to be cut, measured and within arm reach before you turn on the heat. Marinate the proteins with a cornstarch slurry so they sear cleanly without sticking. Blanch dense vegetables in salted water for 60 seconds so they hit the wok already half cooked. Heat the wok dry, off the protein, until a drop of water vaporizes on contact in two seconds.
Cook in small batches. A single chicken thigh-worth of protein per batch is the limit on a home burner. Add the oil, swirl it around the sides of the wok, drop in the protein and do not stir for 30 seconds. Toss once, add aromatics, add sauce, add vegetables. The whole stir fry happens in 3 minutes, and the kitchen should fill with smoke. Open a window first.