Trim the tough ends and split the kai lan in half lengthwise. Wash thoroughly to remove soil and grit. (If you are using another variety of kailan, please read the recipe notes below.) Drain well and set aside.
250 g kai lan
In a small bowl, add the sauce ingredients and stir to combine. Taste and adjust to your preference. In another bowl, mix the cornstarch with the water.
Heat a wok over medium heat. When hot, reduce the heat to low and add the oil. Add the minced garlic and stir continuously until it just begins to turn light golden. Turn off the heat and immediately remove the garlic with a slotted spoon (note: garlic burns quickly once golden and will turn bitter). Leave the garlic-infused oil in the wok.
Heat the wok (with the garlic-infused oil) over high heat. When hot again, add all the vegetables at once and stir-fry vigorously for 1 minute, or until the stalks and leaves just begin to soften and wilt.
Add the sauce and thicken with the cornstarch slurry to your desired consistency (stir the slurry well just before adding). Transfer to a serving plate, top with the fried garlic, and serve immediately.
Notes
#1. Depending on the variety of kailan, you may need to peel away the tougher, fibrous outer layer of the kai lan stalks with a short-bladed kitchen knife. This helps the stalks cook quickly and reduces the risk of overcooking.#2. If you are cooking a long-stemmed variety where the stalks also need cooking, separate the leaves from the stalks. When ready to stir-fry, cook the stalks first until slightly softened, then add the leaves. Alternatively, after peeling off the tough fibrous outer layer, thinly slice thick stalks so the stalks and leaves can be stir-fried together in the hot oil.#3. You can combine the sauce ingredients and the cornstarch slurry in the same bowl, but it is harder to control the final consistency. With experience, you will be able to gauge how much slurry is needed for the amount of sauce you are making.