Cook vermicelli according to package directions. Drain and set aside.
Meanwhile, heat oil in a large pot over medium heat. Add tofu; cook until browned, 2 minutes. Add garlic and ginger and cook about 2 minutes. Add mushrooms, broth, and cabbage and simmer 5 minutes. Stir in reserved noodles. Ladle soup into bowls and add cilantro, onions, and soy sauce.