In a large Dutch oven or soup pot, heat the olive oil over medium-high heat. Once hot, add the sausage and cook for 5 minutes or until browned, breaking it up with a wooden spoon as it cooks. Transfer the sausage to a plate and set aside.
Add the onion, celery, and carrots, then cook for 5 minutes until softened, stirring occasionally. Then, add the garlic and cook for 1 minute until fragrant.
Next, add 2 cans of the white beans, Parmesan rind, Italian seasoning, salt, pepper, and crushed red pepper flakes to the pot.
Pour in the chicken broth and bring the soup to a boil, then reduce the heat to low and simmer for 20 minutes, stirring occasionally.
After 20 minutes, remove the Parmesan rind. Use an immersion blender to blend the soup in the pot to make it creamy. Alternatively, use a blender or food processor to puree the soup in batches, leaving some texture. Return the soup to the pot after blending.
Add the sausage back to the pot. Stir in the remaining can of beans, kale, lemon juice, and parsley. Allow the soup to cook for a few more minutes. Stir in Parmesan cheese. Taste and adjust seasonings, if necessary.
Ladle the soup into bowls and serve with extra Parmesan cheese, if desired.
