Peel and wash the potatoes whole.Cut them into small cubes of about 1 to 1.5 cm.Put them in a large saucepan with the milk and half the pressed garlic clove. Cook over low heat, covered, for 15 to 20 minutes, stirring gently from time to time. In the meantime, in a frying pan, brown the lardons, then add the finely chopped onions and the remaining pressed garlic. Let brown, then add a pinch of nutmeg and the white wine. Cook gently until the wine evaporates.
Preheat your oven to 150°C.
Gently toss the potatoes with the bacon and onion mixture. The milk from the potatoes should have almost evaporated.
In a casserole dish, place the potatoes and bacon. Add the cream and cover with the cheese. For the cheese, cut it in 2 in the thickness then in quarters and put it on the top of the gratin.
Bake for 1 hour so that the gratin cooks gently and all the flavors develop.
Serve as soon as it comes out of the oven so that it is hot, accompanied by a green salad, it will be even better.
