1 Make the marinade/dipping sauce: In a small bowl, combine the soy sauce, lime juice, fish sauce, sriracha, sesame oil, brown sugar, ginger, garlic, and scallions. You will use some of it for the marinade and some for the dipping sauce.
2 Marinate the steak: Place the steak in a shallow dish. Pour 1/3 cup of the marinade over the steak and set the remaining marinade aside to use later as the dipping sauce.
Turn the steak to coat it in the marinade. Let the steak marinate at room temperature for 30 minutes, turning the steak once or twice, or cover it and let the steak marinate for up to 24 hours in the refrigerator.
If you refrigerate the meat, let it come to room temperature before grilling.
3 Cook the rice noodles: Follow the cooking directions on the package of noodles. (Individual manufacturers’ instructions vary.) Drain the noodles in a colander and rinse under cold running water, tossing with your hands, to remove the excess starch and prevent the noodles from sticking together.
4 Grill the steak: Light a charcoal grill or turn a gas grill to high (about 450ºF). Grill the steak for 3 to 5 minutes per side for medium-rare (135ºF). The exact timing will depend upon the heat of the individual grill and the thickness of your steak.
For best results, use an instant read thermometer inserted into the center of the steak: 125ºF for rare, 135ºF for medium rare, 145ºF for medium.
5 Rest and slice the steak: Transfer the steak to a cutting board, cover with foil, and let rest for 10 minutes. Thinly slice it across the grain.
6 Arrange the ingredients on a platter: Tear the lettuce leaves into large pieces, removing the stiff stem ends.
Arrange the lettuce leaves, scallions, radish, cucumbers, peanuts, mint, and cilantro on a large platter around the sliced steak, rice noodles, and dipping sauce. This allows each person to build his or her own wrap.
7 To make one wrap: Set a lettuce leaf on a plate. Place some rice noodles and steak slices over the leaf, and top with scallions, cilantro, mint, radishes, cucumbers, and peanuts. Roll or fold and serve with dipping sauce.