Potatoes with Duck Fat and Rosemary

Ingredients

Wash, dry, and thinly slice the potatoes. No slice should be thicker than 2mm.
Put them in a mixing bowl with the goose or duck fat.
Remove the leaves from the rosemary and chop finely – you should have about 2 tablespoons. Scatter over the potatoes. Set the oven to 180°C fan/gas mark 6.
Peel and thinly slice the garlic, then add to the potatoes with a generous seasoning of salt and black pepper.
Toss the potatoes to evenly coat with the fat and seasoning, then arrange the slices—neatly or hugger-mugger as you wish—in a large roasting tin (about 30cm in diameter). Cover with a lid or a sheet of foil.
Bake for 1 hour, then remove the lid and continue cooking for a further 30 minutes until the potatoes are golden and meltingly soft. (Test with a skewer; it should slide through the layers effortlessly.)
If desired, scatter a few pink peppercorns over the top 10 minutes before they are finished.