Prepare the kailan: Slice off and discard the woody ends and cut in half lengthwise. Wash carefully to remove any grit, then drain well. Set aside.
Make the sauce: In a small saucepan combine the water and cornstarch and mix well to dissolve. Add the remaining sauce ingredients, place over medium heat and whisk while the sauce is coming up to a boil. Cook for 1 to 2 minutes, or until thickened and remove from the stove.
Place a wok on medium heat and when hot, lower the heat to low and add the vegetable oil. Add the garlic and stir-fry it, stirring constantly until the garlic is golden. Remove the fried garlic from the oil with a slotted spoon and set aside.
Lower the heat back to medium and when the wok is hot, add the kailan. Stir-fry for 1 to 2 minutes, or until the kailan softens slightly. Transfer to a serving dish, drizzle with sauce and top with the fried garlic.
Serve immediately.