Ingredients

• 1/4 cup soy sauce
• 1 tablespoon sugar
• 2 teaspoons Asian sesame oil
• 1 bunch scallions (white and pale green parts separated from greens), minced (1/2 cup)
• 1 tablespoon minced garlic
• 1 tablespoon minced peeled fresh ginger
• 3 tablespoons sesame seeds, toasted
• 1 lb flank steak, cut across the grain into very thin slices (no more than 1/8 inch thick)
• 1 tablespoon vegetable oil
• Accompaniments: butter lettuce or other soft-leaf lettuce; thinly sliced garlic; packaged kimchi*; steamed white rice

Instructions

1. Stir together soy sauce, sugar, sesame oil, white and pale green scallions, garlic, ginger, and 2 tablespoons sesame seeds in a bowl until sugar is dissolved. Add steak and toss to coat, then marinate 15 minutes.
2. Heat vegetable oil in a 12-inch heavy skillet over high heat until just smoking, then add steak in 1 layer and sauté, turning over occasionally, until browned and just cooked through, about 5 minutes total. Transfer to a platter and sprinkle with scallion greens and remaining 1 tablespoon sesame seeds, then serve with accompaniments.
3. *Available at Asian markets and many supermarkets.