Trim ends of the Chinese broccoli. Line up the Chinese broccoli with the stems facing same direction. Cut the stalks in half to separate the thick stems from the leaves.
Add one inch of water to a wok, pot or large saute pan and bring to a simmer on medium heat. Layer in the broccoli stems at the bottom of the pan and layer the leaves on top of the stems. You want the thick stems closer to the bottom of the pan so that they will cook faster. Steam for 3 minutes. Use tongs to lift the leaves to a plate. Check the stems to make sure they are cooked - they should be easily pierced with a knife. Thicker stems might need an additional minute.
Discard the remaining water in the pan and wipe dry with a towel. Return pan to the stove and add in the cooking oil and ginger, garlic and chile pepper. Turn the heat to medium-low. Once the oil in the wok begins shimmering, cook for another 15 seconds (take care not to burn the aromatics). Stir in the miso paste, water, soy sauce and sesame oil and cook another 15 seconds. Add the Chinese broccoli back into the pan, give everything a quick stir, then plate for serving.
The broccoli stems are thicker and should go at the bottom of the pan, to cook evenly.Wipe off the water from the wok before you stir in the aromatics, this will prevent splattering.Fresh young Chinese broccoli will have a wet-milky-transluscent-ish color in the center of the stem.You can substitute Chinese broccoli for broccolini. You can also use the same ingredients and sauce for almost all Asian vegetable stir-fries, for example, yu choy. The same seasonings also work for spinach and broccoli.