This is from Americas Test Kitchen
1 1/2 lbs flank steak
1/4 cup soy sauce
1/4 cup vegetable oil
2 tablespoons Asian chili sauce (to taste)
1/4 cup packed dark brown sugar
1/4 cup minced cilantro leaves
2 garlic cloves, minced or pressed through a garlic press
4 scallions, both white and green parts, sliced thin
Cut flank steak in half lengthwise and freeze for 30 minutes.
Combine soy sauce and all other ingredients in a measuring cup, set aside.
Remove flank steak from the freezer and slice each piece across the grain into 1/4 inch thick strips.
Weave meat onto indiviual bamboo skewers.
Dunk meat end of each skewwer in the marinade to coat.
Lay the skewers in a shallow dish, propping up the exposed ends of the skewers to keep them clean.
Pour the remaining marinade over the meat.
Regfrigerate for EXACTLY one hour (any more and the meat will start to get mushy.).
Adjust an oven rack to the top position and heat the broiler.
Lay the skewers in a single layer on a wire rack set over a rimmed baking sheet and cover the skewer ends with foil. (May have to broil 2 different sets.).
Broil 6-7 minutes, flipping the skewers halfway through, until meat is browned.