In large saucepan, bring chicken stock, chicken breasts and bay leaves to boil; reduce heat, cover and simmer for about 20 minutes or until chicken is no longer pink inside. Remove chicken and discard bones; dice meat and set aside. Discard by leaves. Keep stock warm.
Meanwhile, in large skillet, heat 2 tbsp of the oil over medium heat; cook onion, garlic, carrots and celery for 10 minutes, stirring occasionally. Add remaining oil, green pepper, cabbage, thyme and rosemary; cook over low heat, stirring occasionally, for 10 minutes.
Add vegetable mixture to stock in sauce pan along with tomatoes and pepper; bring to boil. Reduce heat, cover and simmer for 30 minutes. Add spinach, parsley, zucchini, kidney beans and reserved diced chicken; cook for 5 minutes. Remove 1 cup (250 ml) of the soup and set aside.
Ladle half of the remaining soup into 24-cup (6L) Dutch oven or casserole; cover with four of the bread slices and 1/2 cup of the Parmesan cheese. Cover with remaining soup; layer with remaining bread. Drizzle reserved soup over top; sprinkle with remaining Parmesan cheese. (Recipe can be prepared to this point, cooled, covered and refrigerated for up to 24 hours.).
Bake, covered in 350°F oven for 20 minutes (45 minutes if refrigerated); uncover and bake for 20 minutes longer (45 minutes if refrigerated) or until hot.
Serve soup in large warmed bowls. Garnish with a drizzle of olive oil and a sprinkle of Parmesan cheese, if desired.