In a large bowl, combine 1 tablespoon soy sauce, the grated ginger, and the next 7 ingredients (through scallions). Mix thoroughly. Add the turkey, and mix lightly with hands to combine. In a stockpot, combine sliced ginger and chicken stock. Bring to a simmer over medium-high heat. Let simmer, covered, 5 minutes.
Uncover pot and drop turkey mixture by tablespoonfuls into simmering stock to make freeform meatballs. Stir very gently to fully submerge meatballs. Add spinach and cook, uncovered, 3 minutes or until meatballs are firm and no pink remains inside (cut one open to check). Add remaining soy sauce.