Method

1. Remove the chicken from the fridge 1 hour before you plan to cook it and discard any packaging. Dry well inside and out with kitchen paper, then stuff the cavity with the lemon you have cut in half and the rosemary.
2. Preheat the oven to 190°C/ 375°F/ Gas Mark 5. 
3. Peel the garlic, then use a garlic crusher or the fine side of a box grater if you find that easier. Mix with one teaspoon of butter in a small bowl until evenly combined and season with a little salt and pepper. Smear all over the skin and put into a roasting tin that it fits snuggly into.
4. Remember to wash your hands with warm soapy water after handling raw chicken.
5. Place the chicken in the oven and roast for 1 hour and 20 minutes until the chicken is cooked through and golden brown. To check that it is fully cooked, pierce the thigh with a skewer - the juices should run clear. 
6. Meanwhile, steam the potatoes in a petal steamer inserted into a saucepan over a medium heat for 15-20 minutes or until completely tender.
7. Meanwhile, peel the turnip and carrots and cut both into small dice, then put into a pan fitted with a petal steamer and place on a medium heat to cook for 8-10 minutes or until just tender.
8. Remove the chicken from the oven and cover loosely with tin foil and a clean tea towel and leave to rest while you cook the vegetables. 
9. Mash the turnip and carrots together until you have a smooth mash, then season with plenty of pepper.
10. Carve the chicken into slices and arrange 100g on each plate with the potatoes and turnip and carrot mash to serve.