1. Heat the olive oil in a large skillet over medium heat. Add the chopped onion, diced carrots, and diced celery. Saute for about 5-7 minutes until the vegetables begin to soften. Stir in the minced garlic and cook for another minute until fragrant. This step helps build a deeper flavor base for your soup.

2. Transfer the sauteed vegetables to your slow cooker. Add the boneless, skinless chicken breasts or thighs, crushed tomatoes, rinsed and drained cannellini beans, rinsed and drained kidney beans, chicken broth, dried oregano, dried basil, and red pepper flakes (if using). Season with salt and black pepper to taste.

3. Stir all the ingredients gently to combine. Cover the slow cooker with its lid and cook on low for 4-6 hours or on high for 2-3 hours. The chicken should be cooked through and easily shreddable when done.

4. Once the cooking time is complete, carefully remove the cooked chicken from the slow cooker. Using two forks, shred the chicken into bite-sized pieces. Return the shredded chicken to the slow cooker.

5. Stir the small pasta into the soup. Continue to cook on high for another 15-20 minutes, or until the pasta is tender to your liking. Keep an eye on it to prevent overcooking.

6. Stir in the fresh spinach until it wilts, which usually takes just a couple of minutes. Taste and adjust seasonings if necessary. Ladle the hot soup into bowls and garnish with fresh parsley or basil and a sprinkle of grated Parmesan cheese, if desired.