Prepare the Base: In your slow cooker, combine the boneless skinless chicken breasts or thighs, diced onion, and minced garlic. Pour in the crushed tomatoes and chicken broth, then sprinkle in the dried basil, oregano, crushed red pepper flakes, salt, and pepper. Stir everything together until well-mixed, ensuring the chicken is submerged in the flavorful tomato base.

Cook the Chicken: Cover the slow cooker and set it to cook on low for 6–7 hours or high for 3–4 hours. Once done, carefully remove the chicken with tongs and let it rest for a few minutes.

Shred the Chicken: Using two forks, shred the cooked chicken into bite-sized pieces. Return the shredded chicken back to the slow cooker, stirring it into the savory broth.

Add the Pasta: Stir in the uncooked small pasta of your choice into the soup. Cover the slow cooker and cook on high for an additional 15–20 minutes until the pasta is al dente.

Incorporate the Cheese: Once the pasta is cooked, stir in the grated Parmesan cheese and shredded mozzarella cheese until melted. You can add heavy cream or half-and-half at this stage if desired.

Serve and Garnish: Ladle the soup into bowls, garnishing with additional cheese and fresh basil or parsley for a bright touch.