When I want to 'hold' this soup, meaning, keep it warm for a long period of time and serve it to a crowd, I reach for my crockpot. I double the recipe, using a full pound of sausage and two cans of beans (everything else is doubled, too). If you have a crockpot that lets you sear, cook the sausage in the crockpot before setting it to slow cook. If not, brown the sausage on the stove, and then pour it in the crockpot. Add all remaining ingredients (except spinach and Parmesan cheese), and cook on LOW for 6 hours.