Heat a large Dutch oven or soup pot over medium-high heat and spray with cooking spray. Remove sausage from casings and add to pan. Cook until browned, 8-9 minutes, using a wooden spoon to break down into bite-sized pieces. Remove from pan and set aside.
In the same pan, add diced onion, carrots and celery. Add a pinch of salt and pepper to get the juices released from the veggies and cook until tender, about 7-8 minutes. Add garlic, chili flakes and bay leaf. Cook for 30 seconds to release flavors then add beans, cooked sausage, broth and diced tomatoes.
Bring pot to a boil then reduce heat to low. Simmer for 30 minutes or until beans are tender.
Serve with chopped parsley and parmesan.
Notes
This recipe makes a very large batch which is intentional. I love freezing half of it for another busy night or saving it for lunch throughout the week. Of course, you can always reduce the recipe in half to avoid leftovers.