Braise the potatoes with a little water, until a toothpick can be easily inserted.

Preheat the oven to 200°C. Butter a tart tin, then crush the potatoes, pressing them well to form a compact base. The thicker the potato layer, the stronger the pie. If the base is too thin, it will be less stable, like in my video because I didn't feel like putting too many potatoes in.

For this, you can use a glass covered with lightly oiled baking paper to prevent sticking and to obtain a perfect result. Once mashed, brush the potatoes with olive oil, then season with salt, pepper and a pinch of nutmeg. Put the base in the oven for 20 minutes at 200°C so that it grills lightly.

Meanwhile, cut the onions into thin strips and brown them in a teaspoon of ghee until they become soft. Then add a tablespoon of maple syrup and a tablespoon of balsamic vinegar. Let the onions cook for another 5 minutes so that they caramelize well.

Remove the potato base from the oven. Mix the crème fraîche with a pressed clove of garlic and finely chopped chives, then spread this mixture directly onto the base. Add the caramelized onions on top, distributing them evenly. Sprinkle the grated Emmental cheese over everything.

Put the tart back in the oven for 15 minutes at 200°C to brown the Emmental cheese. Let the tart cool for a few minutes before cutting it. It will be firmer and easier to serve.