Bring a large pan of salted water to the boil. Add the potatoes and cook for 12-15 mins until tender. Drain , then return to the pan and use a masher to smash them up, but don’t fully mash them.
Heat the fat in the chicken’s roasting tin in the oven. Once hot, add the potatoes. Toss them in the fat and juices, then season generously. Return the tin to the oven and roast for 20 mins.
Remove from the oven and mix in the spring onions. Return to the oven for 5 mins before serving.