2 pounds flank steak, trimmed
½ cup soy sauce
¼ cup packed dark brown sugar
3 tablepoons Sriracha chili sauce
2 tablespoons sesame oil
2 tablespoons tahini (sesame paste)
2 teaspoons grated peeled fresh ginger
2 teaspoons black pepper
Pat the steak dry with paper towels. Cover tightly with plastic wrap; place on a baking sheet, and freeze until almost firm, 1 to 2 hours. (Do not freeze steak solid.)
Combine the soy sauce, brown sugar, Sriracha, sesame oil, tahini, ginger, and pepper in a large ziplock plastic freezer bag.
Cut the meat in half horizontally, making two thin slabs of steak. Slice the meat against the grain into ¼ inch strips. Add to the ziplock bag with marinade; toss to coat. Seal the bag, and refrigerate 3 to 24 hours, turning occasionally.
Let the meat stand at room temperature in the bag 1 hour before baking. Preheat the oven to 175°F. Line two rimmed baking sheets with aluminum foil; fit each baking sheet with a wire rack sprayed with cooking spray. Remove the meat strips from the marinade, draining and blotting the excess marinade. Arrange the strips on the prepared racks, leaving about ¼ inch between each strip.
Bake in the preheated oven until the meat strips are completely dry, very dark in color, and break apart (depending on the desired degree of chewiness) when gently bent, 4 to 5 hours.