Stir-Fried Beef and Bok Choy

Name: Stir-Fried Beef and Bok Choy
Yield: Serves 4
Cuisine: Asia, Asian
Ingredients: 1 (1½-pound), flank steak, trimmed; 1/4 cup, oyster sauce; 2 tablespoons, cornstarch; 2 tablespoons, soy sauce; 1/2 teaspoon, baking soda; 1/4 cup, water; 2 tablespoons, packed brown sugar; 2 tablespoons, toasted sesame oil; 4 , scallions, white and green parts separated and sliced thin; 2 , garlic cloves, minced; 8 small heads, baby bok choy (1½ to 2 ounces each), halved