Combine tamari, brown sugar, rice vinegar, and chile-garlic sauce (if using) in small bowl, and set aside.Heat oil in large wok or skillet over high heat. Add onion, and stir-fry 1 to 2 minutes, or until softened. Add broccoli and carrots, and stir-fry 3 minutes, or until crisp-tender. Add mushrooms, bell peppers, and cashews, and stir-fry 3 to 4 minutes, or until vegetables are tender. Add garlic and ginger, and stir-fry 30 seconds. Add sauce, and stir-fry 1 minute. Sprinkle with green onions.