This decadent dish was invented years ago as a way to use up excess Reblochon, a creamy Alpine cheese. Ultimately, it's just a simple dish of bacon, onions, potatoes, cream and the cheese, but the result is indulgent and out of this world.
Preheat oven to 425 degrees F and set a pot of salted water to boil. Melt 1 tablespoon of butter in a saucepan on medium heat. Add the onion slices and bacon to the pan and sweat until the onions are translucent and the bacon is cooked. Do not brown. Season with pepper. Meanwhile, cook the potatoes in the simmering water for twenty minutes, or until cooked but still slightly firm. Drain and let cool. Peel then cut the potatoes into rounds.
Butter the casserole dish. Layer the dish with half of the cooked potatoes; lightly season with salt and pepper. Make a layer with half of the onion and bacon mixture. Repeat the layering process with the rest of the potatoes and onion/bacon mixture. Cut cheese into long strips (including the rind) and layer it over the casserole, covering fully. Pour the cream over the casserole. Bake until cheese is melted and golden, about 25–30 minutes.
Remove casserole from oven, spoon onto plates, and serve.