First heat the oil in a frying pan and, when it's really hot, fry the walnuts until they are golden brown – this should take about 1 minute. Then, remove them to a plate and allow to cool.
Now you need to chop the pork rashers roughly and add them to the bowl of a processor, along with the chicken livers. Process until coarsely chopped into pieces resembling the turkey mince. Remove them to a large bowl, then add the turkey mince and pancetta (or bacon), along with 1 rounded teaspoon of salt, the mace, garlic and walnuts.
Next, crush the peppercorns and juniper berries lightly with a pestle and mortar and add these as well. Next, pour the wine and brandy over, then you really have to give everything a very thorough mixing. You can do this with a large fork, or even your hands but, either way, make sure that everything is thoroughly mixed together and all the flavours are evenly distributed.
Then, cover the bowl with a cloth and leave it in a cool place for a couple of hours.
When you are ready to cook the terrine, pre-heat the oven to gas mark 2, 300°F (150°C), and boil the kettle.
Pack the mixture into the loaf tin and place it in a roasting tin. Pop the roasting tin in the oven on the middle shelf, then pour in enough boiling water to come halfway up the loaf tin. Now bake the terrine, uncovered, for about 2½ hours.
When it is cooked it will have shrunk away from the sides of the tin and there will be a lot of fat swimming around. All you do is remove it from the oven but leave the fat. Don't worry – you are not going to have to eat it, but it is necessary because, as the terrine cools down, this surrounding fat will keep it moist.
Then, as soon as it is completely cold, place a double strip of foil across the top, followed by a piece of stiff card, and weight it down. If you have scale weights, these will be ideal. If not, you can use tins of tomatoes or something similar. This is essential, as it packs the terrine closely together, making it very easy to slice. Pop it in the fridge, weights and all, and leave it there until you need to serve it.
To serve the terrine, loosen it all the way around the edges with a palette knife and turn it out on to a carving board.
It will look very messy at this stage, but all you do is scrape off all the fat and jelly surrounding it, wipe with kitchen paper, then cut it into slices and serve with the toasted bread and cranberry confit.