Preheat the oven to 180°C.
Heat the oil in large, heavy-based casserole dish and cook the sausages until brown.
Meanwhile peel the shallots.
Transfer the sausages to a plate, then fry the bacon and shallots in the same pan for 5 minutes. Sprinkle them with the cornflour, then slowly pour in the cider, while stirring continuously. Add the bay leaf, thyme leaves and garlic. Bring to the boil.
Cover the dish with a lid or foil, then put it in the oven for 30 minutes.
Meanwhile, core the apple and cut it into thin rings. Brush them with some oil.
Remove the lid, add the apple, and bake for another 20-30 minutes, turning the sausages and apple slices a couple of times.
Serve the sausages, shallots and apple slices with the cooking jus.