1. In a soup pot, heat the oil over medium-high heat. Add the garlic, ginger and chicken. Cook 2 to 3 minutes, stirring occasionally, until chicken is no longer pink on the outside.
2. Dissolve the peanut butter in the crushed tomatoes; add the mixture to the soup pot along with the chicken broth and fish sauce and bring to a boil. Add the noodles; reduce heat to a gentle simmer and cook 5 minutes. Stir in the cabbage and cook another 5 minutes. Stir in the bean sprouts and scallions; turn off heat.
3. Ladle soup into bowls and top each with cilantro and peanuts if desired.