Brown the Sausage: Heat a skillet over medium heat and cook the ground Italian sausage until browned and crumbled, about 5–6 minutes.Drain excess fat if needed. Build the Slow Cooker: Add the browned sausage, diced onion, carrots, celery, minced garlic, white beans, chicken broth, tomatoes if using, Italian seasoning, smoked paprika, salt, pepper, and bay leaves to the slow cooker. Stir everything together to distribute the ingredients and seasonings evenly. Slow Cook the Soup: Cover and cook on low for 6–7 hours or on high for 3–4 hours, until the vegetables are tender.
Add the Kale: Stir the chopped kale into the soup during the final 20–30 minutes of cooking. Continue cooking until the kale is wilted and tender without becoming mushy. Prepare the Parsley Dressing: Combine the finely chopped parsley, olive oil, lemon juice, grated garlic, and a pinch of salt in a small bowl. Stir well to combine.
Finish the Soup: Remove the bay leaves from the slow cooker.Stir in the freshly grated Parmesan and heavy cream, if using. Taste the soup and adjust the salt and pepper as needed. Garnish and Serve: Ladle the hot soup into bowls, sprinkle with additional Parmesan, and spoon the fresh parsley dressing over the top. Serve with crusty bread. Store: Allow the soup to cool completely, then transfer it to an airtight container and refrigerate for 3–4 days.
Freeze: Allow the soup to cool completely before transferring it to freezer-safe containers or bags. Freeze for 4–6 months and label the container or bag with the preparation date.