Note 1: See notes for Crock Pot method.Note 2: The mustard powder and hot sauce are so subtle in this soup but help enhance the other flavors, so although you may be hesitant to add them, I highly recommend it!
Remove the casings from the sausage if you purchased links. Preheat a large pot over medium heat. Add the sausage and cook and crumble to break it apart. Once cooked halfway through, reduce heat to medium-low and cover partially. (This is the best way to ensure you get drippings). Continue to heat, stirring occasionally, until cooked through. It’ll take around 10-12 minutes total.
Set the sausage aside on a paper towel lined plate. Reserve 1 tablespoon drippings. (Butter can be used if you don’t have drippings.)
Add the drippings to the pot along with 2 tablespoons butter over medium heat. Add the diced onions, celery, and carrots and cook for 4 minutes. Add the garlic and cook for 1 minute.
Add the flour and cook for 1-2 minutes to remove the raw flour taste.
Add the hot sauce, Worcestershire sauce, seasonings, and beans.
Add the chicken broth and use a silicone spatula to “clean” the bottom of the pot, this will add more flavor to the soup. Bring to a boil, reduce to a simmer.
Simmer for 20 minutes, then add the sausage back. Simmer for 15 more minutes, then add the spinach and let it wilt for 2-3 minutes.
Stir in ¼ cup heavy cream if desired. Transfer to serving bowls and top with grated Parmesan cheese.