Preheat the oven to Gas Mark 4, 180°C (350°F).
Place the loin of bacon in an ovenproof saucepan along with the carrot, celery and vinegar. Cover with cold water, bring to a boil and simmer for 30 minutes. While the bacon is cooking, in a small bowl combine the ingredients for the topping - juniper berries, garlic, sage leaves and honey.
After 30 minutes remove the bacon from the saucepan and place on a plate or board. Score the fat and spread over the topping mixture. Discard the cooking liquid and vegetables and rinse the saucepan with cold water. Return the bacon to the saucepan, add the cider and place, uncovered, in the preheated oven. Roast for a further 20 minutes basting from time to time.
Remove the bacon from the saucepan and keep warm. Add the crème fraîche to the juices and simmer to reduce for 5 minutes. Whisk in the mustard. If you like the sauce thicker, whisk in the cornflour and water mixture and allow to cook for a couple of minutes.
Meanwhile melt the butter in a wok or large frying pan over a medium heat. Add the sliced onion and garlic and allow it to soften for a few minutes. Add the shredded cabbage, season with a little salt and black pepper and stir-fry for 3-4 minutes until the cabbage is tender and slightly wilted.
Slice the bacon and serve with the cider sauce, stir-fried cabbage and mashed potatoes.