Put the sausages into a large nonstick pan and drizzle with the oil. Cook over a medium heat for 5–6 minutes, stirring them every now and then to prevent them from sticking and burning.
Peel and dice your onion and leek and finely slice the celery, if using . Dice your swede or potato and carrots.
Add all the veg to the pan and extra oil, if required. Season with a pinch of salt. Cook for 10 minutes more, stirring every now and then.
Pour over the cider, wait a beat for it to settle, then add most of the water and the stock cube, mustard and stuffing mix. Drain and thoroughly rinse the beans, then add those too.
Bring to the boil, then reduce to a simmer and cover. Cook for 25 minutes until the sausages and veg are cooked through and the sauce is thick and succulent. Add the remaining water, if required.
Finish with a dash of vinegar or lemon juice, and serve.