Trim ends from Chinese broccoli, then cut in half crosswise, separating the leaves from the stalks. If any stalks are thick, cut them in half lengthwise.
Heat about 1-inch of water in a large lidded pot or wok, bring to boil. Lay stems in an even layer over the boiling water and place leaves across the top. Cover and steam 3 to 5 minutes, to desired tenderness.
With a slotted spoon, transfer broccoli to ice bath.
While the broccoli cools, prepare the dressing. Combine garlic, ponzu sauce, and sriracha sauce in a small bowl then slowly drizzle in sesame oil, whisking constantly. Set aside.
Transfer cooled broccoli with a slotted spoon to a serving bowl. Pat dry with a clean kitchen towel or paper towels.
Drizzle dressing over broccoli and toss to coat evenly. Serve.