1. Prepare noodles according to the package directions and rinse well. Set aside.
2. In a large pot, add chicken stock and miso paste. Whisk together.
3. Add garlic, ginger, and soy sauce and bring the mixture to a simmer.
4. If using raw chicken, add it now and simmer it gently for five to seven minutes or until cooked through.
5. If using leftover chicken, add it with the spinach and simmer until the spinach is wilted.
6. Add the noodles to the pot and taste-test; adjust the flavor with more soy sauce or tamari as needed.