Layer Slow Cooker Base: Place diced onions, carrots, and celery into the bottom of a 6-quart slow cooker. Lay chicken breasts evenly on top. Season with kosher salt, black pepper, and poultry seasoning. Scatter butter cubes over chicken.

Add Broth & Soup: In a medium bowl, whisk cream of chicken soup with chicken broth until smooth, then pour over chicken and vegetables. Ensure chicken is mostly submerged.

Slow Cook: Cover with the lid and cook on LOW for 6 hours (or on HIGH for 3 to 4 hours) until chicken is fall-apart tender and vegetables are soft.

Shred Chicken: Remove chicken breasts to a cutting board, shred into bite-sized pieces with two forks, and return back into the slow cooker broth.

Prepare Biscuit Dumplings: Cut each raw biscuit round into 6 to 8 small bite-sized pieces. Toss pieces lightly with 2 tablespoons of flour in a bowl so they don't clump together. Gently drop the flour-dusted biscuit pieces across the bubbling top of the stew. Press down slightly so they are coated in liquid, but do not stir.

Cook Dumplings & Serve: Cover tightly with lid and cook on HIGH for an additional 60 to 75 minutes without opening the lid (to trap the steam). Dumplings will swell into fluffy, pillowy clouds and cook through the center. Fold in frozen peas during the last 5 minutes. Garnish with fresh chopped parsley and cracked black pepper before serving hot.