Preheat the oven to 200°C/gas mark 6. Open the turkey cavity and place the onion, celery, lemon and half the thyme inside. Rub the butter all over the skin of the turkey then put it on a rack in a large roasting tin and cook in the oven for 20 minutes, uncovered.
Meanwhile, finely chop the reserved thyme leaves. Put the brandy, honey and sugar into a saucepan and bring to the boil, before simmering for 2-3 minutes until reduced slightly. Stir in the thyme.
After the turkey has been cooking for 20 minutes, brush liberally with the glaze. Turn the oven down to 180°C/gas mark 4. Cook for another 20 minutes, brush again, then cover with strong foil. Roast in the oven for another 3 hours, basting every 30 minutes with the glaze. Remove from the oven and ensure the juices run clear, before allowing to rest under a loose tent of foil while you assemble the rest of the meal.
Pour 100ml boiling water over the porcini mushrooms and leave for 10 minutes. Grease a baking tray with a little butter and preheat the oven to 200°C/gas mark 6. Heat the butter in a large frying pan and cook the onion for 2-3 minutes, until beginning to soften. Add the garlic and cook for another minute.
Put the speciality and chestnut mushrooms in the pan and cook for 4-5 minutes, or until golden. Drain the soaked porcini mushrooms and roughly chop, then add these to the pan along with the madeira. Bubble for 2 minutes before removing from the heat and allowing to cool.
Stir in the sage, thyme, breadcrumbs and parmesan to the cooled mixture. Stir through the egg to bind, then divide the mixture into 8. Roll into balls and place on the greased baking tray. Bake in the oven for 20-25 minutes or until golden. Serve on a platter and carve.