Step 1: Prepare the Slow Cooker - Spray an eight quart slow cooker generously with non stick cooking spray. This helps prevent sticking and makes cleanup much easier later.
Step 2: Season the Chicken - Lay the chicken breasts evenly across the bottom of the slow cooker. Sprinkle the garlic salt, onion powder, and paprika evenly over the chicken so every piece is well seasoned.
Step 3: Mix the Stuffing Layer - In a large bowl, combine the chicken broth, chicken stuffing mix, and chicken gravy. Stir until everything is evenly moistened and combined. Spread this mixture evenly over the seasoned chicken.
Step 4: Add the Creamy Layer - In a medium bowl, stir together the sour cream and cream of mushroom soup until smooth. Spread this mixture gently over the stuffing layer, covering it completely.
Step 5: Slow Cook - Cover the slow cooker and cook on low for five to six hours. The chicken will become tender and the casserole will thicken beautifully as it cooks.
Step 6: Add the Green Beans - During the last hour of cooking, add the frozen green beans and gently spread them throughout the casserole. Replace the lid and continue cooking until the beans are heated through.
Step 7: Finish and Serve - Once fully cooked, scoop the casserole onto plates and sprinkle crispy fried onions on top if using. Serve warm and enjoy every comforting bite.