Preheat your oven to 400°F (200°C) to ensure it’s hot enough to create a bubbly crust.

Peel the potatoes and cut them into thin slices.

In a large pot, bring salted water to a boil and add the potato slices. Cook for about 10 minutes until just tender but not fully cooked. Drain and set aside.

While the potatoes are cooking, heat a skillet over medium heat. Add the lardons and cook until crispy, about 5-7 minutes. Remove the lardons and let them drain on a paper towel.

In the same skillet, sauté the finely chopped onion in the remaining fat until soft and translucent, about 3-4 minutes.

In a greased baking dish, layer half of the potato slices, followed by half of the onion and lardons. Season with salt and pepper.

Pour half of the cream over this layer and sprinkle half of the cheese, cut into slices.

Repeat the layers with the remaining ingredients: potatoes, onions, lardons, cream, and the rest of the cheese on top.

Bake for around 25-30 minutes, until the cheese is bubbly and golden brown.