1 Cut the steak with the grain into 2-inch-wide strips. Then cut each strip across the grain into 1/4 inch-thick slices.
2 In a medium bowl, combine the steak with 1 tablespoon of the soy sauce and the cornstarch. Stir to coat the steak and set aside.
3 Cut the carrots on the diagonal into 1/4 inch-thick slices (if desired, use a french-fry cutter to give the carrots a ripple design). If the mushrooms are small, leave them whole; otherwise, halve them. Cut the scallions into 2-inch lengths.
4 In a small bowl, combine the broth, remaining 1 tablespoon soy sauce, the hot pepper sauce and black pepper.
5 In a large skillet or wok, warm 1 tablespoon of the oil over medium-high heat until hot but not smoking. Add the scallions, garlic and ginger. Stir-fry for a few seconds. Add the carrots and mushrooms and stir-fry until the carrots are crisp-tender, 3 to 5 minutes. Remove the vegetables to a plate and cover loosely to keep warm.
6 Add the remaining 1 tablespoon oil to the skillet and warm over medium-high heat until hot but not smoking. Add the steak and the marinade and stir-fry until the steak is browned but still slightly pink in the center, 2 to 3 minutes.
7 Return the vegetables to the skillet. Stir the broth mixture, add it to the skillet and bring the liquid to a boil. Cook, stirring constantly, until the vegetables are tender and the beef is cooked through, 2 to 3 minutes longer.
8 Stir in the cilantro (if using)