Warm the confit duck legs over a gentle heat to release the fat, then pour the fat into clean jam jars. You will need some for this dish, but save the rest for roasting potatoes another day.
Remove the skin from the duck legs and discard it or slice and roast as a nibble. Pull away the duck meat with a couple of forks and shred it, removing and discarding any bones and gristle.
Heat two tablespoons of the duck fat in a pan, add the shallots, thyme and half a teaspoon of peppermix or plenty of black pepper. Allow the shallots to brown gently and once they are golden, add the wine and stock, then bring to the boil.
Cook for a few minutes, then add the duck meat and the chopped parsley. Stir and set aside.
Preheat the oven to 210°C/Fan 190°C. Boil the potatoes in salted water for 20–25 minutes until tender. Drain them well, then add the warm milk and mash until smooth. Season with salt and a big pinch of peppermix or some black pepper.
Grease a baking dish measuring about 18 x 28cm with duck fat. Pile in the meat mixture, then cover with mashed potatoes. Sprinkle the grated cheese on top and bake for about 25 minutes until heated through and browned on top.
Serve with a green salad, green beans with garlic and fried breadcrumbs or carrots à la fermière.