Preheat the oven to 190°C, fan 170°C, gas 5. Place the chicken in a roasting tray and roast, following pack instructions, until cooked through and no pink remains. Pour the oil in another roasting tin and heat in the oven.
Place the potatoes in a pan of cold water. Bring to the boil and cook for 7 minutes, then drain and shake in the pan. Gently pour into the heated roasting tray and mix to coat in the oil. Roast for 1 hour, turning once or twice.
Meanwhile, mix the cheese, spinach and breadcrumbs in a bowl and season. Place in a lightly oiled dish and bake with the chicken for the last 10 minutes.
Boil the carrots for 6 minutes, then add the peas and cook for 3 minutes, then drain. To make the gravy, mix 2 tablespoons of the chicken juices with the flour over a medium heat. Gradually add the stock and bring to the boil, stirring. Serve with the roast chicken and veg. Keep the leftover chicken to use in sandwiches.
Cook's tip: Try swapping the chicken for halved, deseeded butternut squashes. Fill with the stuffing and roast for 45-50 minutes.