Place the bok choy in the top of a steamer basket over simmering water. Cover and steam the bok choy until tender, about 10 minutes.
Measure the soy sauce, chicken broth, rice vinegar, oyster sauce, sugar and sesame oil into a measuring cup. Set aside.
Cook the garlic and ginger in a small skillet sprayed with nonstick cooking spray over medium heat just until tender, about 1 minute. Stir in the soy mixture. Bring to a simmer and cook 1 minute.
Pour the ginger sauce on a platter, then arrange the steamed bok choy on the platter. - Updated: November 30, 2007