Preheat the oven to 200°C/180°C fan/400°F. Peel the potatoes and slice them into ½ cm rounds. Put them into a saucepan of cold salted water, place over the heat and bring to the boil. Cook until partially done but tender, around 10 minutes. Drain and set aside.
Meanwhile, finely slice the onion. Cook the slices in butter over medium heat for 5 minutes, season with salt and pepper, then once soft add the wine to deglaze the pan. Continue to cook the onions until the wine has evaporated.
At the same time, in another frying pan, cook the lardons for 5 minutes until golden.
Take a deep-sided baking dish and tip in half the onions then cover with half of the lardons. Layer all the potato on top then repeat with the remaining onions and lardons.
Cut the wheel of cheese in half through the middle so that you have two thinner rounds. Slice the rounds into quarters, and place them, cut-side down, rind up, on the onions and lardons. Cut the cheese into smaller pieces to fill spaces where you can.
Slide the dish into the oven and bake for 30 minutes until the cheese is gold and bubbling. Serve with green vegetables if you want to feel healthy.