Place chicken, butter, cream of chicken soup, and onion in a slow cooker. Cover and cook on High for 5 to 6 hours. Stir in carrots after 5 hours of cooking.
Place torn biscuit dough in slow cooker 30 minutes before serving. Cook until dough is no longer raw in the center, about 25 minutes. Lift edges of biscuits and stir in peas. Let stand until warm, about 10 minutes, before serving.