Place the chicken breasts in the slow cooker. Add the white beans, onion, garlic, carrots, thyme, salt, pepper, and chicken broth.
Cover and cook on low for 6 hours or on high for 3 hours, until the chicken is fully cooked and tender.
Remove the chicken from the slow cooker and shred it with two forks. Return the shredded chicken to the pot.
Stir in the chopped kale. Cover and cook for 15 more minutes until the kale wilts.
While the kale cooks, preheat the oven to 375 degrees. Toss the bread cubes with olive oil and Parmesan cheese on a baking sheet.
Bake the bread cubes for 10 to 12 minutes, stirring once, until golden and crisp.
Ladle the soup into bowls and top each serving with a handful of Parmesan croutons.