Wash and peel the potatoes, then cook them in a large pot of salted water for about 15 minutes. Drain and let cool before slicing into rounds.

Cook the bacon in a skillet until crispy, about 5-7 minutes. Remove and set aside. In the same skillet, sauté the sliced onion for 5 minutes until soft.

Preheat the oven to 400°F (200°C). Layer the sliced potatoes, onion, bacon, cream, and Reblochon cheese in a baking dish, repeating the layers.

Bake the dish for 25-30 minutes until the top is golden and bubbling.

Let the dish rest for about 5 minutes before slicing and serving.