Preheat oven to 400°F/200°C/Gas 6 Method: Wash the giblets in cold water, place in a large pan with 1.5 litres of cold water. Bring to the boil and removed any scum of the top of the water with a slatted spoon. Then add the rest of the ingredients, cover and simmer for 40 minutes.
Uncover the pan and simmer for a further 20-30 minutes or until the stock has reduced by half. Remove from the heat and strain into a bowl, leave to cool, cover and place in the fridge or use immediately.
To make the gravy, bring the stock back to the boil and remove from the heat. When the turkey is cooked pour off the fat from the roasting juices, place the tin on the hob, whisk in the flour and place over a low heat and cook the flour mixture making sure you have scrapped up all the meaty sticky bits, on the bottom of the tin and stir constantly.
After 2 minutes, remove from the heat and whisk in the turkey giblet stock and redcurrant jelly, bring slowly to the boil, stirring constantly. Add the sherry and cook for a further 3 minutes, stirring constantly.
Season to taste add a little more sherry if you want and then strain into a warm jug and serve. Any leftover turkey sherry gravy can be frozen.
The giblet stock can be made 2 days before required.