In a bowl combine the tablespoon rice vinegar, minced fresh ginger, 1/2 teaspoon salt and teaspoon sesame oil. Marinate the chicken in this mixture for 30 minutes. During this time soak rice noodles in warm water to cover for 10 minutes; drain and set in colander.
When you are ready to eat combine broth, garlic clove, remaining tablespoon rice vinegar and sesame oil and bring to a boil. Add soaked rice noodles and cook for 5 minutes. Remove garlic clove. Add the marinated chicken to the broth and simmer for 1 to 2 minutes or until just cooked through. Add the spinach and remove from heat when spinach is wilted. Season to taste with salt and pepper. Ladle out soup.
Recipe courtesy of Michele Urvater