Combine ingredients for marinade in a baking dish or shallow bowl. Marinate the beef and let sit for 15 minutes to 1 hour at room temperature, or overnight in the refrigerator.
Meanwhile, make Lime Dipping Sauce:
Stir sugar and salt into the lime juice until well dissolved. Add the rest of the ingredients and mix well. Set aside at room temperature until ready to serve.
Heat up a large saute pan or small wok until hot; very high heat is required so that the meat will cook quickly without bleeding out too much juice. Add soybean oil, sugar, garlic, and black peeper and stir to caramelize for 30 seconds, being careful not to burn the garlic and black pepper. Add marinated beef and stir very quickly over very high heat for 2 minutes. Add mushroom soy sauce and stir to cook for another 2 minutes or so. Cook the beef to desired doneness; it's best served medium-rare to medium.
Garnish a large plate with the young lettuce leaves. Plate the loc lac beef in the middle. Sprinkle with scallion greens. Serve with jasmine rice and Lime Dipping Sauce on the side.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.