Place all ingredients except for spinach and parsley in a large stock pot, bring to a boil, reduce heat, cover, and let simmer for at least 25 minutes, ideally 1 hour or more.
Add spinach and parsley, let simmer for 5 - 10 minutes. Strain liquid for your broth needs and reserve veggies to add to another soup, stew, or make a pureed veggie soup!
Let the broth cool, store in the fridge for up to a week and make sure to freeze any leftovers!