For the paste filling, either put all the ingredients in a small food processor and blend until well combined (it doesn’t have to be completely smooth), or pound with a pestle and mortar.
Lay the pork out, skin-side down, and rub the paste over the pork, then roll it up as tightly as you can and secure at intervals with butcher’s twine.
If you have time leave in the fridge, uncovered or loosely wrapped in kitchen towel overnight – or even better, for two nights, to give the flavours time to permeate the meat and to let the skin dry out.
An hour before you are ready to start cooking the pork, remove it from the fridge so it can return to room temperature. Preheat the oven to 150C/130C Fan/Gas 2.
Arrange the potatoes and onion slices on the base of a large roasting tin and season with salt. Pour over the white wine (or cider) and stock (or water).
Make sure the rind of the pork is dry and season it with salt. Place on top of the potatoes and onions. Cover with foil and put in the oven. Roast for four hours until the pork is cooked through – the internal temperature should read 68C/154F (use a meat thermometer to check this).
Turn the heat up to its highest setting and cook for a further half an hour to crisp up the skin. Remove from the oven and transfer the meat and potatoes to separate serving dishes. Leave the meat to rest for half an hour, uncovered, but keep the potatoes warm.
To make the spiced apple sauce, put all the ingredients in a saucepan with a splash of water, then cook gently for around 10 minutes, or until the apples have softened and broken down into a purée. Taste and adjust the flavours if necessary – you may need a little more sugar.
To finish the pork, strain off any liquid remaining in the tin and skim off any fat. Serve the juices alongside the meat and potatoes.