1
Position rack in upper third of oven; preheat broiler. Rub steak all over with soy sauce and black pepper. Place on a baking sheet; broil, turning once, 14 to 16 minutes for medium-rare to medium, respectively. Let rest on a cutting board for 5 minutes.
2
Meanwhile, mix scallions, lime zest and juice, fish sauce, sugar and crushed red pepper in a shallow dish. Slice the steak into thin strips against the grain and cut each strip into bite-size pieces. Add the steak to the marinade, along with any accumulated juices; toss well, cover, and refrigerate overnight.
3
Place frisee (or endive), lettuce and mint in a salad bowl. Add the steak and marinade, drizzle with oil, gently toss, and serve.
