1. Cook noodles according to package directions, about 8 to 10 minutes, omitting salt and fat. Drain and divide among 4 large serving bowls.
2. Combine water, soy sauce, mirin, vinegar, and ginger in a small saucepan over medium heat; bring to a simmer. Add tofu or steak; simmer 4 minutes or until cooked through.
3. Divide lettuce, radish, carrot, and green onions among the bowls. Ladle hot broth and tofu or steak over noodles.
4. Drizzle each serving with a few drops of hot sauce and sesame oil, if desired.
Nutritional analysis with beef: Calories 547 (24% from fat); Fat 15g (sat 5g, mono 7g, poly 1g); Cholesterol 68mg; Protein 43g; Carbohydrate 59g; Sugars 8g; Fiber 5g; Iron 5mg; Sodium 973mg; Calcium 62mg