Remove the wish bone from the crown of the turkey.
Put the sausage meat into a bowl. Melt the butter, sweat the onion for two minutes, do not colour.
Add the sage to the onion and cool for two minutes. Pour into the sausage meat, add breadcrumbs and season. Stuff the turkey with the stuffing from the neck end
Put the excess stuffing into an ovenproof dish and bake separately at 200 celsius for 1 hour.
Lay the turkey on its side in the roasting tray and support the breast using a potato and cook at 200°celsius for 30 minutes. Remove from the oven and turn it over onto other leg and cook for a further 30 minutes.
Remove from the oven, sit on the turkey on its back to finish cooking, for approximately another 30 minutes.
Test to see if the meat is cooked by piercing the legs to see that the juices run clear.
Take out the oven and rest for roughly 15 minutes. Serve with the roast potatoes and brussel sprouts.