Place chicken breasts in the bottom of the slow cooker.

In a small bowl, whisk together the garlic parmesan sauce, milk, minced garlic, and black pepper.

Pour the sauce mixture over the chicken.

Cover and cook on LOW for 4 hours until chicken reaches an internal temperature of 165 degrees Fahrenheit.

Remove chicken from the slow cooker and shred or cut into bite-sized pieces, then return it to the pot.

Cook the penne pasta in a separate pot according to package directions until al dente.

Drain the pasta and add it to the slow cooker.

Stir in shredded parmesan cheese and baby spinach until the cheese is melted and spinach is wilted.

Garnish with chopped parsley before serving.