Method:
Combine tamari, sesame oil, mirin, rice vinegar, tofu and red pepper flakes, tossing gently to coat. Cover and marinate for 1 to 2 hours. Drain in a colander over a bowl, reserving the marinade.
Heat the canola oil in a wok or large skillet over medium-high heat. Add tofu and stir-fry for 5 minutes, until lightly browned on all sides. Remove tofu and set aside. Add broccoli, carrots and water chestnuts and stir-fry for 5 minutes or until just crisp-tender. Add green beans and stir-fry for 2 minutes. Add green onions, ginger, and garlic and stir-fry for 1 to 2 minutes more, until aromatic. Return tofu to wok.
Combine vegetable broth with arrowroot powder and reserved marinade, stirring well to completely dissolve the arrowroot. Add this to the wok and stir until sauce thickens. Season to taste with black pepper and garnish with cilantro.