Remove the sausage casing.
Heat olive oil in a soup pot over
medium heat and add sausage, stirring to break up the meat into small crumbles. Brown
the meat and remove some of the sausage fat by blotting with a paper towel. Add onion,
celery, and garlic. Sauté briefly. Add beans, chicken broth, bay leaf, and tomatoes.
Heat thoroughly by bringing to a low boil.
Just before serving, add the escarole or
spinach and stir until just wilted (it should stay a vibrant green).