Combine the Fontina/gruyere/Gouda cheese with the parmesan in a bowl, then preheat the oven to 200C/180C fan.
Add the chopped Savoy cabbage to a large saucepan and boil in the stock for about five minutes before turning off the heat.
Heat a little oil in a large frying pan. Fry the bacon pieces until golden and starting to crisp. Remove the crispy bacon bits from the pan and set aside.
Add the butter and more oil to the frying pan and return to the heat. Fry the pieces of bread until golden and crisp on all sides, then set them aside.
Using a slotted spoon, transfer half of the cabbage from the stock to a large casserole dish placed on the stove. Season with plenty of pepper and a little salt, and add half of the bread, half of the bacon and half of the cheese.
Repeat with more cabbage, bacon, and bread and season with salt and pepper.
Finally, ladle over the hot stock and finish with the remaining cheese.
Bring the contents of the dish to a simmer, transfer to the oven, and bake uncovered for 30 to 40 minutes until hot and bubbling, with all the cheese melting.
Serve the soup fresh from the oven in four bowls.
