Pinch off each leaf, including the stem, from the main stalk and any other tender parts of the vegetables. Wash and rinse thoroughly a couple of times and set aside to drain off any excess water before cooking.
Heat the oil in a wok over medium heat. Add the garlic and ginger, and cook for about a minute. Now turn the heat to high, and add in the sweet yam leaves.
Stir and add in the sesame oil, Shaoxing wine (optional), ground white pepper, water, salt (to taste) and a pinch of sugar. Stir to cook for a couple of minutes until all the leaves are wilted. Serve immediately.