Heat the duck fat in a large casserole and add the sausages and boudin noir. Cook until browned all over. Remove the sausages and boudin noir from the pan and set aside covered on a plate in the fridge.
Add the onions, garlic, juniper berries, thyme sprigs, caraway seeds, bay leaves and apples to the pan. Pour in the wine and cook until the volume of liquid has reduced slightly.
Add the pork shoulder, the whole piece of bacon and the stock. Simmer, covered for 2 hours until tender. Put the sausages and boudin back into the pan and add the sauerkraut and the potatoes. Simmer for 20–30 minutes.
To serve, slice the meat and serve it alongside the sauerkraut and potatoes.