Trim the bok choy stems and separate the leaves. Rinse and dry them thoroughly.
In a small bowl, whisk together the soy sauce, vegetable broth, rice wine vinegar, brown sugar, vegetable oil and garlic.
Place a wok or large skillet with high sides over medium-high heat. Add the soy sauce mixture and cook, stirring, until the garlic is fragrant, about 1 minute.
Add the bok choy, cover the wok and cook for 2 minutes. Uncover the wok, increase the heat to high and continue cooking until the bok choy is tender and the sauce thickens slightly, about 1 more minute.
Top the bok choy with toasted sesame seeds and serve.