Preheat the oven to 190°C/375°F/gas 5 and oil a 20cm baking dish.
Peel and finely chop the onions, pick the sage leaves, then peel and chop the parsnips and apples into 1cm chunks.
Heat a lug of oil in a large non-stick pan over a medium heat, add the onion and sauté for 5 to 10 minutes, or until softened but not coloured.
Meanwhile, shred the sage and add to the pan along with the parsnips, cider and a good pinch of sea salt and black pepper.
Place a lid on the pan and leave for 10 minutes to soften the parsnips. Remove the lid, add the apple and cook for another couple of minutes, then spoon the mixture into a bowl and allow to cool completely.
Once cool, snip the ends off the sausages and squeeze the meat out of the skins into the bowl.
Tear the bread into a food processor and blitz to breadcrumbs, then tip into the bowl. Crack in the egg and finely grate in the lemon zest.
Using your hands, scrunch it all together until well combined, then press into the prepared baking dish, cover with tin foil and bake for 45 minutes. Remove the foil, cook for a further 15 minutes, then serve.