Wash the spinach well, then dry completely. Heat a wok or heavy-bottomed frying pan on medium high, then add the oil. When the oil is hot, add the garlic. Stir for a minute until the garlic releases its aroma, but don’t let it brown. Add the dry spinach and stir-fry constantly for about two minutes, moving the soften leaves to the top, until nearly all the leaves are just barely wilted. Quickly mix in the soy sauce, sesame oil, salt, if used, and a pinch of pepper. As soon as blended, remove from the heat before the spinach gets too soft and mushy. Taste and add more pepper or salt as you like. Sprinkle with sesame seeds and serve immediately. This dish is also good leftover warmed or cold on its own or in eggs or with noodles, rice or other leftover protein and vegetables. *Cook proteins and/or other vegetables in the pan first, then remove them before adding the other ingredients; return them to the pan to finish the dish.