1. 1/4 cup soy sauce
2. 2 teaspoons freshly ground pepper
3. 1/4 cup minced fresh lemongrass (from 2 stalks)
4. One 2 1/2-pound flank steak
5. 3 tablespoons fresh lime juice
6. 2 tablespoons Asian fish sauce
7. 1 tablespoon crushed red pepper
8. 1/2 teaspoon sugar
9. 2 medium shallots, thinly sliced
10. 1/2 cup mint leaves
11. 1/4 cup cilantro leaves
12. 2 teaspoons roasted rice powder (optional; see Note)

1. In a large glass baking dish, mix the soy sauce with the pepper and 2 tablespoons of the lemongrass. Add the flank steak and turn to coat. Let stand at room temperature for 30 minutes.
2. Light a grill. Grill the flank steak over moderately high heat, turning once, until charred on the outside but still pink within, about 8 minutes. Transfer the steak to a carving board and let stand for 5 minutes. Cut the steak in half lengthwise. Slice the halves across the grain 1/4 inch thick.
3. In a large wok or nonreactive skillet, combine the lime juice with the fish sauce, crushed red pepper, sugar and the remaining 2 tablespoons of lemongrass. Cook over moderate heat until hot. Stir in the sliced steak along with 1 tablespoon of the marinade. Add the shallots, mint, cilantro and roasted rice powder, stirring to coat. Transfer the salad to plates and serve.

Notes Roasted rice powder, also known as khao kua pon in Thailand, is available at Asian markets but can also be made at home. In a skillet, toast raw glutinous (sticky) rice over low heat, stirring occasionally, for 30 to 45 minutes. Transfer to a mortar or spice grinder and let cool. Grind the rice to a powder.