Place chicken breasts or thighs in the slow cooker, then add diced onion, minced garlic, crushed tomatoes, and chicken broth. Sprinkle in dried basil, oregano, red pepper flakes (if desired), salt, and pepper. Stir gently to combine.

Secure the lid and cook on low for 6-7 hours or on high for 3-4 hours until the chicken is tender.

Remove the chicken, shred it using two forks, then return it to the soup.

Stir in uncooked pasta, cover, and cook on high for 15-20 minutes until pasta is al dente.

Stir in grated Parmesan and shredded mozzarella until melted. Add heavy cream or half-and-half if desired.

Ladle soup into bowls, topping with extra cheese and garnishing with fresh basil or parsley.