Storage: Store leftovers in airtight containers in the refrigerator for up to 3 days. Reheat gently over low heat, adding a splash of milk if the soup has thickened too much.
Substitutions: You can use vegetable broth instead of chicken stock for a vegetarian version. Swallow cheddar or mozzarella can replace Jarlsberg if unavailable.
Variations: For a creamier spinach soup, add an extra half cup of heavy cream. Add a pinch of nutmeg to the spinach soup for extra warmth.