Preheat your oven to 200°C (392°F).
Cook the potatoes in salted boiling water for about 10 minutes, or until just tender. Drain and set aside.
In a frying pan over medium heat, cook the bacon lardons until crispy. Remove from the pan and set aside.
In the same pan, add the sliced onions and cook until they are soft and translucent. Add crushed garlic and cook for an additional 1-2 minutes.
In a large baking dish, layer the potatoes, onions, and bacon.
Add crème fraîche over the top and season with salt and pepper.
Add the cubes of Reblochon cheese on top of the mixture.
Bake in the preheated oven for 20-25 minutes or until golden and bubbling.
Remove from the oven and let it cool slightly before serving.