Add the onion, carrots, celery, garlic, cannellini beans, diced tomatoes, vegetable broth, Italian seasoning, bay leaf, and olive oil to the slow cooker.
Stir gently, cover, and cook on low for 6 hours.
Stir in the chopped kale, replace the lid, and cook for 30 more minutes until the greens are tender.
Remove the bay leaf, taste, and add salt and black pepper as needed.
Ladle into bowls, top with fresh parsley, and serve with crusty bread.