Heat the oil or fat in a casserole dish and brown the sausages all over so they get a good colour. Remove them with a slotted spoon and set aside then put the lardons, shallots and potatoes in the pan and brown them all over as well (the potatoes don’t need to get much colour).
Add the garlic and cook for another minute, then add the brandy and allow it to bubble away. Pour in the white wine, stock, thyme and bay.
Place the sausages back in the casserole dish, season lightly, bring everything to a boil then turn the heat down low, cover and cook for 20 minutes.
Add the prunes, turning them over with the other ingredients so they are well mixed in. Simmer for another 10 minutes, this time with the lid off so that the cooking liquid can reduce.
Melt the butter in a small frying pan and quickly sauté the chestnuts, adding the sugar and tossing everything around until the sugar caramelises the chestnuts slighty.
Add these to the pot and cook for another five minutes. Check the seasoning. Stir in some chopped fresh thyme leaves and serve.Serve with cabbage on the side.