Two packets of gravy mix is not a typo. One leaves it thin. If the gravy is thicker than you like, loosen it with a splash of warm broth just before serving.
Instructions
Lay the chicken breasts in a single layer in the bottom of a 6-quart slow cooker.
Whisk the gravy packets, cream of chicken soup, broth, garlic powder, and pepper until smooth, then pour over the chicken.
Cover and cook on LOW for 4 hours, until the chicken reaches 165°F and pulls apart easily.
Shred the chicken with two forks right in the gravy and stir to coat. Let it sit 5 minutes to thicken.
Taste for salt, scatter parsley over the top, and serve over mashed potatoes.