Add chicken breasts, chicken broth, garlic, Italian seasoning, salt, pepper, and butter to the slow cooker.
Cover and cook on LOW for 3–4 hours or until chicken is tender and cooked through.
Remove chicken, shred or slice it, and set aside.
Add uncooked penne pasta and heavy cream to the slow cooker. Stir well, cover, and cook on HIGH for 20–30 minutes.
Stir once halfway through to prevent pasta from sticking.
Once pasta is cooked, stir in Parmesan cheese until melted and creamy.
Return chicken to the slow cooker and stir gently to combine.
Garnish with parsley before serving, if desired.
Notes
For extra richness, stir in 2 oz cream cheese with the Parmesan.You can add spinach or steamed broccoli in the last 5 minutes.Avoid using pre-shredded cheese—it won’t melt as smoothly.