Step 1: Place chicken breasts in the bottom of a 6-quart crockpot.
Step 2: In a medium bowl, whisk together cream of chicken soup, cream of mushroom soup, chicken broth, sour cream, onion, garlic, Italian seasoning, salt, pepper, and paprika until smooth.
Step 3: Pour the sauce mixture over the chicken in the crockpot.
Step 4: Cover and cook on LOW for 6 hours or on HIGH for 3 hours, until chicken is tender and cooked through.
Step 5: Remove chicken from crockpot and shred with two forks.
Step 6: Return shredded chicken to the crockpot and stir in broken spaghetti, cheddar cheese, and Parmesan cheese.
Step 7: Cover and cook on HIGH for 30-45 minutes, until spaghetti is al dente and sauce is creamy, stirring once halfway through.
Step 8: Let rest for 5 minutes, then garnish with fresh parsley if desired before serving.