Preheat the oven to 220C/425F/Gas 7. Remove all the clumps of excess fat from the inside of the goose cavity. Put them into a pan with a little sunflower oil and leave on a very low heat until melted, then pass through a fine sieve into a bowl. (This makes a beautiful frying medium for the roast potatoes, and chips too.)
For the stuffing, fry the onions in about 75g/3oz of the goose fat until soft and very lightly browned. Stir into the breadcrumbs with the lemon zest, sage, parsley and plenty of salt and pepper to taste. Stir in enough beaten egg to bind the mixture together.
Weigh the goose and calculate the cooking time, allowing 14 minutes per 450g/1lb. Season the cavity of the goose with salt and pepper and then spoon in the stuffing. Seal the opening with a metal skewer.
Season the skin of the goose with salt and place it on a rack set over a large roasting tin. Roast the goose for 30 minutes. Remove it from the oven and lower the temperature to 180C/350F/Gas 4. You need to pour off the excess fat from the roasting tin. The easiest way to do this is to lift the goose onto a board with two clean tea towels (you don't want to pierce the skin by using forks), pour off the fat into a bowl and then replace the goose on the rack. Return it to the oven and roast it for a further 1 hour 50 minutes. Pour off more fat after another 30 minutes.
In the meantime, for the gravy, fry the bacon, giblets and vegetables in a little goose fat until golden brown. Pour off the excess fat, add the water, bay leaves and peppercorns and simmer for 1 hour. Strain through a sieve and set aside.
Peel the potatoes, cut them into large chunks and boil them for 7 minutes in water salted at the rate of 1 teaspoon per 600ml/1 pint. They should be soft on the outside but still slightly hard in the centre. Drain well, then shake them around in the pan with a lid on to give the edges a sandy texture. After the goose has been cooking at the lower temperature for 1 hour, remove from the oven and lift it and the rack off the roasting tin. Add the potatoes to the tin and turn them over so that they all become well-coated in the fat. Pour off any excess fat, replace the goose and continue to roast for the remainder of the cooking time.
When the goose is cooked, the juices from the thigh should run clear when pierced with a skewer. Lift it onto a board, cover it with foil and leave it to rest for at least 20 minutes. Turn the potatoes over if necessary, return the roasting tin to the oven and increase the oven temperature to 220C/425F/Gas Mark Roast the potatoes for approximately another 20 minutes or until crisp and golden. Remove and transfer to a serving dish. Turn off the oven and return the dish of potatoes to the oven to keep warm. Set the roasting tin over a source of heat, add the giblet stock and deglaze the tin by rubbing the base with a wooden spoon. Season to taste and pass through a sieve into a gravy boat.
For the apple sauce, put the prepared apples and water into a pan and simmer for 12-15 minutes, stirring now and then, until soft and smooth. I like to serve it unseasoned. Keep warm.
Not being a very neat carver, I like to carve in the kitchen and take the slices of goose to the table on a large warm plate. (Cut off the legs and cut each one in half, then carve the breast meat away from each side into long, thin slices). I serve the stuffing, apple sauce and gravy separately, with some sprouts, the roast potatoes and the swede, carrot and potato purée.