Ingredients:

1/2 cup soy sauce
1/4 cup rice vinegar
3 scallions, white and 2 inches of the green parts, finely chopped
Additional chopped scallions for garnish
2 tablespoons firmly packed brown sugar
1 (2-inch) piece fresh ginger, finely chopped
1 1/2 tablespoons Asian toasted sesame oil
2 teaspoons hot red pepper flakes
1 1/2 pounds skirt steak
Vegetable oil for sauteing the beef
Salt and freshly ground black pepper


Combine the soy sauce, vinegar, scallions, sugar, ginger, sesame oil, and pepper flakes in a bowl. Whisk well to blend. Reserve 1/4 cup and set aside. Pour the rest into a plastic bag with a resealable closure. Add the skirt steak and seal. Marinate in the refrigerator, turning the bag often, for at least 4 hours or overnight. Remove the skirt steak from the marinade and pat dry with paper towels. (The drier the beef, the better it will sear.) Working in batches, heat half the oil in a large skillet over high heat until almost smoking. Season the meat with salt and pepper. Place in the skillet and reduce the heat to medium-high. Cook until seared on the outside and rare to medium-rare on the inside, 2 to 3 minutes per side. Transfer to a platter, cover loosely with foil, and let rest for 5 minutes. Repeat with the remaining oil and skirt steak. Cut into very thin slices, holding the knife at an angle and cutting against the grain. Toss with the reserved 1/4 cup sauce in a large bowl until well coated.
Serve with noodles or rice.