How to Make It
In a small bowl, combine the broth with the oyster sauce, wine, soy sauce, sugar and salt.
Set a large wok over high heat. When it's hot, add the oil and swirl to coat. After 20 seconds, add the scallions, garlic and ginger and stir-fry for 30 seconds. Add the choy sum and stir-fry for 2 minutes; press it against the wok, then stir and press again. Add the sauce in the bowl and bring to a boil, then cover and simmer for 3 minutes. Add the cornstarch mixture and continue stir-frying until the sauce thickens, about 15 seconds. Transfer the greens to a small platter and serve hot.