This luxurious dish is made with tenderloin of beef to ensure that it's perfectly tender and melt-in-your-mouth delicious. A simple Vietnamese-inspired sauce imparts flavor, while broccoli adds both color and crunch. The beef needs to marinate for at least 1 hour before cooking, so be sure to plan accordingly. Adding a touch of sugar to the beef before cooking ensures it will caramelize lightly, and a knob of butter introduced at the finishing stage mellows the sauce and thickens it slightly. Serve with jasmine rice.
Combine two tablespoons of the oil, 1 teaspoon of the sugar, and the pepper in a medium bowl and whisk to blend. Add the beef and toss to coat the cubes of meat. Cover with a plate and let the meat marinate at room temperature for 1 hour, or up to 4 hours in the refrigerator.
Meanwhile, steam the broccoli until it’s crisp-tender. Drain and plunge the florets into a bowl of ice and water to stop the cooking process and set their bright color. When cool, drain thoroughly and set aside.
In a small bowl, whisk together the soy sauce, lime juice, vinegar, fish sauce, the remaining sugar, ginger, and garlic. Set aside.
Just before serving, remove the beef from the marinade and pat the cubes of meat dry with paper towels. Heat a large 12- or 14-inch skillet (preferably cast-iron) over high heat. When the skillet is very hot, add 1 tablespoon of the oil and tilt the pan to film the bottom of the skillet evenly with the oil. Add half of the beef (to avoid crowding the pan). Cook, turning the cubes with tongs to sear all sides, until the meat is cooked to your liking, about 3 minutes for medium-rare. Add half of the scallions, half of the butter, and one third of the soy-lime sauce. Stir-fry for 30 seconds, then transfer the contents of the skillet to a warm platter. Repeat with the remaining oil and beef, then add the rest of the scallions, butter, sauce, and reserved broccoli to the skillet. Cook until the broccoli is heated through, about 1 minute, and transfer the mixture to the platter. Serve hot.