Pick young tender leaves off the plant and discard the stem. Wash thoroughly, then drain the greens in a colander and set aside. Heat the vegetable oil in a wok over high heat until just reaching smoking point. Add the garlic slices to the wok and stir-fry until they just turn brown. About two minutes. Put the sweet potato greens in the wok and stir-fry for another minute or so. At this point the leaves will be wilted. Add the rest of the ingredients and continue to stir-fry for another minute. Plate the vegetables and serve immediately.