In a mixing bowl, whisk together soy sauce, oyster sauce, sesame oil, and sugar until well combined.
Add the cubed beef, garlic, shallot, and pepper to the marinade. Toss to combine and let stand in refrigerator for an hour.
When ready to cook, heat a wok over high heat. Add two tablespoons of olive oil around the top of the wok, letting it run down the side and into the middle of the wok. Add half of the beef mixture to the wok in a single layer and sear for 3 minutes. Shake and toss the mixture in the wok and cook for another minute or two. The beef should be seared on all sides. Transfer to a plate and keep warm.
Add the rest of olive oil and repeat with the remaining beef mixture.
When ready to serve, arrange the watercress and cherry tomatoes on a plate and top with the beef mixture and juices.
For the dipping sauce, stir together salt, pepper, and lime juice.
Serve the shaking beef with the dipping sauce.