How to Make It
Combine the chicken broth, ginger and garlic in a medium soup pot and bring to simmer over moderate heat. Reduce heat to moderately low and continue to simmer for 15 minutes. Discard the ginger and garlic.
Meanwhile, cook the soba noodles in a large saucepan of boiling water until al dente, about 4 minutes. Drain and rinse under cold water until cooled. Shake out the excess water and set aside.
Stir the soy sauce into the broth; taste and add a little more if needed. Add the tofu and cabbage and simmer until the cabbage is crisp-tender, 6 to 8 minutes.
Stir in the peas and soba noodles and simmer until heated through. Ladle the soup into bowls and garnish with the sliced scallions.