- Preheat oven to 425°F. Spray large roasting pan with nonstick spray.
- Prick sausage all over with fork and transfer to medium skillet. Add enough cold water to cover and bring to boil. Reduce heat and simmer until sausage is firm, about 5 minutes. Drain, cool slightly, and cut into 1/2-inch slices.
- Combine parsley, thyme, garlic, 3/4 teaspoon of salt, and 1/2 teaspoon of pepper in small bowl. Place chicken, breast side down, on cutting board. Using kitchen shears or knife, cut through ribs on each side of backbone and discard. Turn chicken over and use your hands to flatten chicken. Gently lift skin from chicken and spread herb mixture evenly under skin. Place chicken in center of prepared pan. Tuck wing tips under chicken.
- Scatter apples, onion, and sausage around chicken. Sprinkle apple mixture with remaining 1/4 teaspoon salt and remaining 1/4 teaspoon pepper; lightly spray with nonstick spray. Roast until instant-read thermometer inserted into chicken thigh (not touching bone) registers 165°F, 50–55 minutes, stirring apple mixture once halfway through roasting time.
- Transfer chicken and apple mixture to platter and cover to keep warm. Strain pan juices into measuring cup. Add cider to roasting pan and set over two burners. Bring to boil over high heat, scraping browned bits from bottom of pan. Cook, stirring occasionally, until cider is reduced by half, about 6 minutes. Strain cider mixture into measuring cup and skim off visible fat. Carve chicken into 8 pieces and serve with apple mixture and sauce. Remove chicken skin before eating.
- Per serving: 1 piece chicken with 1/2 cup apple mixture and about 2 tablespoons sauce
Look for local apple cider, which is simply unfiltered apple juice, at farmers' markets. The flavor of the cider will vary from farm to farm or even week to week depending on the types of apples used.