Begin by marinating the beef slices to infuse them with flavor and tenderize the meat. Combine 1 teaspoon soy sauce, 1 teaspoon Chinese rice wine, 1/2 teaspoon cornstarch, and 1/8 teaspoon black pepper in a medium bowl. Add the sirloin steak slices and stir thoroughly until each piece is evenly coated. Allow the beef to rest for 10 minutes, giving the marinade time to penetrate. Next, prepare the sauce by mixing 2 tablespoons oyster sauce, 1 teaspoon Chinese rice wine, 1 tablespoon soy sauce, and 1/4 cup chicken broth in a small bowl. Set this savory mixture aside; it will bring your stir-fry together. For the broccoli, bring a pot of water to a vigorous boil. Add the broccoli florets and blanch them for about 2 minutes, just until they become crisp-tender. Drain thoroughly to avoid excess water diluting the sauce later. Heat a large frying pan or wok over high heat until a bead of water flicked onto the surface vaporizes instantly. Pour in 2 tablespoons of high-heat cooking oil and swirl it around to coat the pan evenly. Add the marinated beef to the hot pan, spreading it out in a single layer without overlapping. Let the meat sear undisturbed for 1 minute to develop a beautiful brown crust. Flip the slices over, sprinkle in the minced garlic, and stir-fry for an additional 30 seconds to 1 minute until the beef loses its pinkness and the aroma of garlic is released. Avoid overcooking to keep the beef tender. Now, pour in the prepared sauce along with the cornstarch slurry (1 teaspoon cornstarch dissolved in 1 tablespoon water). Stir continuously as the sauce bubbles and thickens rapidly, coating the beef attractively. Finally, toss the crisp broccoli into the pan and mix until evenly heated. Serve your Beef and Broccoli Stir-Fry immediately, ideally paired with steaming bowls of jasmine rice. For an added touch, garnish with toasted sesame seeds or sliced scallions. Enjoy a delightful balance of flavors and textures in every bite!