Wash and drain gailan thoroughly. Trim 1 inch off the end of the stalks. Cut off each leave from the stalk and then cut the leave into 2 or 3 bite size pieces at a diagonal, about 2 to 3 inches in length. Cut the top part of the remaining stalk into bite size pieces as well, leaving the remaining end of 3 to 5 inches. This woody section should be peeled with a paring knife before cutting diagonally into bite size pieces. Stems and leaves should preferably be separated.
Heat a wok or large pan. When it is hot, add vegetable oil. Sauté ginger for about 1 minute. Stir in garlic for 30 seconds.
Add the gai lan stems and mushrooms (if using). Fry for about 2 minutes.
Now, add the gai lan leaves, soy sauce, and Shao Hsing cooking wine. Stir fry for 1 to 2 minutes. gai lan leaves should be wilted but still crunchy.
Pour in cornstarch mixture. Stir to combine for another 1 to 2 minutes. Corn starch mixture will thicken.
Turn off heat. Drizzle sesame oil over vegetables. Remove and serve immediately.