Step 1

Cut beef with the grain into 2-inch-wide strips. Cut each strip across the grain into 1/4-inch-thick slices. Combine the beef, ginger, soy sauce, 1 tsp. sherry, and cornstarch in a medium bowl; stir until the cornstarch is no longer visible. Add sesame oil and stir until the beef is lightly coated.

Step 2

Combine oyster-flavored sauce and the remaining 1 Tbsp. sherry in a small bowl. Set aside.

Step 3

Heat a 14-inch flat-bottomed carbon-steel wok (or a 12-inch stainless-steel skillet) over high heat until a drop of water vaporizes within 1 to 2 seconds of contact. Swirl in vegetable oil. Add the beef in an even layer; cook, undisturbed, until it begins to brown, about 1 minute. Using a metal spatula, stir-fry until lightly browned but not cooked through, 30 seconds to 1 minute more. Transfer to a plate.

Step 4

Add bok choy and broth to the pan. Cover and cook until the bok choy greens are bright green and almost all the liquid has been absorbed, 1 to 2 minutes. Return the beef to the pan, add the reserved sauce, and stir-fry until the beef is just cooked through and the bok choy is tender-crisp, 30 seconds to 1 minute.