Rinse and prep your cabbage, kale, and broccoli. To help remove pesticides, soak in a big bowl of cold water and baking soda (Google for proper ratio). Rinse well and drain.
Heat a wok or large deep skillet over high heat until it just starts to smoke. Add the oil and garlic, then toss in the broccoli. Let it cook for about 1–2 minutes, stirring occasionally.
Next, add the cabbage and kale. Give it all a good toss and sprinkle in some salt. Keep stir-frying, moving the veggies around so they hit the hot sides of the pan and get that nice sear.
Once the pan starts looking a bit dry, gather the veggies into the center and pour in ¼ to ½ cup of water (use less if your pan doesn’t hold heat well). Cover the pan and steam for about 2 minutes.
Drizzle in the oyster sauce, if using, and stir everything to coat. Taste and add a pinch more salt if needed. If you prefer softer veggies, give it another minute on the heat.
Serve warm alongside your chicken!