Proper roast chicken

Ingredients

1 whole chicken: 3 lb 5 oz to 4 lb (giblets removed)
Butter: 1 oz (softened)
Lemon: ½ unwaxed lemon
White wine or vermouth: 3½ fl oz (optional, used in the roasting tin)
Salt and freshly ground black pepper
Stuffing
Butter: ½ oz
Onion: 1 large (finely chopped)
Lemon zest: ½ lemon
Fresh sage leaves: 5 leaves (finely chopped) or 1 tsp dried sage
Fresh breadcrumbs: 3½ oz
Egg: 1 medium egg (beaten)

The Gravy
Plain flour: 1 tbsp
White wine: 3½ fl oz
Chicken stock: 10 fl oz

Cooking Instructions
1. Make the Stuffing
Melt the ½ oz of butter in a small pan over a low heat. Cook the chopped onion for 5 minutes until soft and translucent.Stir in the lemon zest and sage, then cook for 1 more minute.Take the pan off the heat. Stir in the 3½ oz of breadcrumbs and the beaten egg to bind it all together. Season with salt and pepper.
2. Stuff and Prep the Chicken
Preheat your oven to 400°F (Convection/Fan: 350°F, Gas Mark
Pack the stuffing into the neck end of the chicken, or loosely into the main cavity (leave a tiny bit of space for air circulation)
Weigh the chicken after it is stuffed. Calculate your cooking time based on this total weight: 20 minutes per pound, plus an extra 15 minutes total.
Sit the chicken in a roasting tin. Rub the 1 oz of butter all over the breast and legs, season generously with salt and pepper, and squeeze the juice of ½ a lemon over the top.
Pour your 3½ fl oz of wine and 3½ fl oz of water
3. Roast the Chicken
Roast at the high heat (400°F) for 15 minutes to crisp up the skin.Turn the oven down to 350°F (Convection/and finish roasting for the remaining time you calculated in step 2.Check it is done by piercing the thickest part of the thigh with a skewer—the juices should run completely clear.Move the bird to a warm board and let it rest for 15–20 minutes loosely covered in foil before carving.
4. Make the Gravy
Skim the excess fat from the juices left in your roasting tin.
Put the tin directly on the stovetop over low heat, sprinkle in 1 tbsp of flour, and scrape up all the sticky, caramelized bits from the bottom to form a paste.
Pour in the 3½ fl oz of white wine, let it bubble, and whisk until thick. Gradually whisk in the 10 fl oz of chicken stock along with any extra juices that have run off the resting chicken. Simmer for 2–3 minutes, strain into a jug, and serve