Preheat the oven to 350°F/180°C.
Place the bread cubes in a single layer on a baking sheet and toast in the oven until they take on some color. (You can do this on top of the stove in a large skillet if you prefer). Set aside to cool.
Heat the butter in a large skillet over medium heat. Add the bacon and cook until the pieces just start to brown.
Stir in the onion, celery and apple. Cook until the vegetables are tender, about 10 minutes.
Add the sherry and seasonings and continue to cook until most of the liquid is gone. Remove from the heat.
In a large mixing bowl beat the eggs, cream and chicken stock together with about half of the cheese.
Add the toasted bread cubes and the cooked vegetables and combine.
Allow to stand for about 30 minutes to absorb all of the liquid.
Transfer to an 8 or 9 inch square baking dish that has been prepared with cooking spray and transfer the mix into the pan. Use a spatula to distribute the bread cubes evenly.
Bake for 45 minutes or so or until the custard is set. It's ready when a knife inserted into the center comes out clean.
Remove from the oven and sprinkle with the remaining cheese. Cover loosely with foil or a clean kitchen towel and allow the cheese to melt before cutting into pieces to serve.