For convenience, use shredded rotisserie chicken with the skin removed, or cook and shred chicken breasts or thighs in advance for meal prep. If you prefer an even richer soup, substitute chicken bone broth for regular broth or add an extra tablespoon of butter. To keep the spinach vibrant and tender, always add it at the very end of cooking and avoid prolonged boiling. This soup thickens slightly as it cools, so you can thin leftovers with a splash of broth or cream when reheating. Store cooled soup in an airtight container in the refrigerator for up to 5 days or freeze for up to 2 months, reheating gently over low heat and avoiding a hard boil to prevent the dairy from separating.